Technology Blog : Hadoop , Big Data Interview Questions

What is BIG DATA?

Big Data is nothing but an assortment of such a huge and complex data that it becomes very tedious to capture, store, process, retrieve and analyze it with the help of on-hand database management tools or traditional data processing techniques.

What is Hadoop?

Hadoop is a framework that allows for distributed processing of large data sets across clusters of commodity computers using a simple programming model.

Why the name ‘Hadoop’?

Hadoop doesn’t have any expanding version like ‘oops’. The charming yellow elephant you see is basically named after Doug’s son’s toy elephant!

Why do we need Hadoop?

Everyday a large amount of unstructured data is getting dumped into our machines. The major challenge is not to store large data sets in our systems but to retrieve and analyze the big data in the organizations, that too data present in different machines at different locations. In this situation a necessity for Hadoop arises. Hadoop has the ability to analyze the data present in different machines at different locations very quickly and in a very cost effective way. It uses the concept of MapReduce which enables it to divide the query into small parts and process them in parallel. This is also known as parallel computing.

Can you give some examples of Big Data?

There are many real life examples of Big Data! Facebook is generating 500+ terabytes of data per day, NYSE (New York Stock Exchange) generates about 1 terabyte of new trade data per day, a jet airline collects 10 terabytes of censor data for every 30 minutes of flying time. All these are day to day examples of Big Data!

Can you give a detailed overview about the Big Data being generated by Facebook?

As of December 31, 2012, there are 1.06 billion monthly active users on facebook and 680 million mobile users. On an average, 3.2 billion likes and comments are posted every day on Facebook. 72% of web audience is on Facebook. And why not! There are so many activities going on facebook from wall posts, sharing images, videos, writing comments and liking posts, etc. In fact, Facebook started using Hadoop in mid-2009 and was one of the initial users of Hadoop.

According to IBM, what are the three characteristics of Big Data?

According to IBM, the three characteristics of Big Data are:
Volume: Facebook generating 500+ terabytes of data per day.
Velocity: Analyzing 2 million records each day to identify the reason for losses.
Variety: images, audio, video, sensor data, log files, etc.

How Big is ‘Big Data’?

With time, data volume is growing exponentially. Earlier we used to talk about Megabytes or Gigabytes. But time has arrived when we talk about data volume in terms of terabytes, petabytes and also zettabytes! Global data volume was around 1.8ZB in 2011 and is expected to be 7.9ZB in 2015. It is also known that the global information doubles in every two years!

How analysis of Big Data is useful for organizations?

Effective analysis of Big Data provides a lot of business advantage as organizations will learn which areas to focus on and which areas are less important. Big data analysis provides some early key indicators that can prevent the company from a huge loss or help in grasping a great opportunity with open hands! A precise analysis of Big Data helps in decision making! For instance, nowadays people rely so much on Facebook and Twitter before buying any product or service. All thanks to the Big Data explosion.

Who are ‘Data Scientists’?

Data scientists are soon replacing business analysts or data analysts. Data scientists are experts who find solutions to analyze data. Just as web analysis, we have data scientists who have good business insight as to how to handle a business challenge. Sharp data scientists are not only involved in dealing business problems, but also choosing the relevant issues that can bring value-addition to the organization.

What are some of the characteristics of Hadoop framework?

Hadoop framework is written in Java. It is designed to solve problems that involve analyzing large data (e.g. petabytes). The programming model is based on Google’s MapReduce. The infrastructure is based on Google’s Big Data and Distributed File System. Hadoop handles large files/data throughput and supports data intensive distributed applications. Hadoop is scalable as more nodes can be easily added to it.

Give a brief overview of Hadoop history.

In 2002, Doug Cutting created an open source, web crawler project.
In 2004, Google published MapReduce, GFS papers.
In 2006, Doug Cutting developed the open source, Mapreduce and HDFS project.
In 2008, Yahoo ran 4,000 node Hadoop cluster and Hadoop won terabyte sort benchmark.
In 2009, Facebook launched SQL support for Hadoop.

Give examples of some companies that are using Hadoop structure?

A lot of companies are using the Hadoop structure such as Cloudera, EMC, MapR, Hortonworks, Amazon, Facebook, eBay, Twitter, Google and so on.

What is the basic difference between traditional RDBMS and Hadoop?

Traditional RDBMS is used for transactional systems to report and archive the data, whereas Hadoop is an approach to store huge amount of data in the distributed file system and process it. RDBMS will be useful when you want to seek one record from Big data, whereas, Hadoop will be useful when you want Big data in one shot and perform analysis on that later.

What is structured and unstructured data?

Structured data is the data that is easily identifiable as it is organized in a structure. The most common form of structured data is a database where specific information is stored in tables, that is, rows and columns. Unstructured data refers to any data that cannot be identified easily. It could be in the form of images, videos, documents, email, logs and random text. It is not in the form of rows and columns.

What are the core components of Hadoop?

Core components of Hadoop are HDFS and MapReduce. HDFS is basically used to store large data sets and MapReduce is used to process such large data sets.

What is HDFS?

HDFS is a file system designed for storing very large files with streaming data access patterns, running clusters on commodity hardware.

What are the key features of HDFS?

HDFS is highly fault-tolerant, with high throughput, suitable for applications with large data sets, streaming access to file system data and can be built out of commodity hardware.

What is Fault Tolerance?

Suppose you have a file stored in a system, and due to some technical problem that file gets destroyed. Then there is no chance of getting the data back present in that file. To avoid such situations, Hadoop has introduced the feature of fault tolerance in HDFS. In Hadoop, when we store a file, it automatically gets replicated at two other locations also. So even if one or two of the systems collapse, the file is still available on the third system.

Replication causes data redundancy then why is is pursued in HDFS?

HDFS works with commodity hardware (systems with average configurations) that has high chances of getting crashed any time. Thus, to make the entire system highly fault-tolerant, HDFS replicates and stores data in different places. Any data on HDFS gets stored at atleast 3 different locations. So, even if one of them is corrupted and the other is unavailable for some time for any reason, then data can be accessed from the third one. Hence, there is no chance of losing the data. This replication factor helps us to attain the feature of Hadoop called Fault Tolerant.

Since the data is replicated thrice in HDFS, does it mean that any calculation done on one node will also be replicated on the other two?

Since there are 3 nodes, when we send the MapReduce programs, calculations will be done only on the original data. The master node will know which node exactly has that particular data. In case, if one of the nodes is not responding, it is assumed to be failed. Only then, the required calculation will be done on the second replica.

What is throughput? How does HDFS get a good throughput?

Throughput is the amount of work done in a unit time. It describes how fast the data is getting accessed from the system and it is usually used to measure performance of the system. In HDFS, when we want to perform a task or an action, then the work is divided and shared among different systems. So all the systems will be executing the tasks assigned to them independently and in parallel. So the work will be completed in a very short period of time. In this way, the HDFS gives good throughput. By reading data in parallel, we decrease the actual time to read data tremendously.

What is streaming access?

As HDFS works on the principle of ‘Write Once, Read Many‘, the feature of streaming access is extremely important in HDFS. HDFS focuses not so much on storing the data but how to retrieve it at the fastest possible speed, especially while analyzing logs. In HDFS, reading the complete data is more important than the time taken to fetch a single record from the data.

What is a commodity hardware? Does commodity hardware include RAM?

Commodity hardware is a non-expensive system which is not of high quality or high-availability. Hadoop can be installed in any average commodity hardware. We don’t need super computers or high-end hardware to work on Hadoop. Yes, Commodity hardware includes RAM because there will be some services which will be running on RAM.

What is a Namenode?

Namenode is the master node on which job tracker runs and consists of the metadata. It maintains and manages the blocks which are present on the datanodes. It is a high-availability machine and single point of failure in HDFS.

Is Namenode also a commodity?

No. Namenode can never be a commodity hardware because the entire HDFS rely on it. It is the single point of failure in HDFS. Namenode has to be a high-availability machine.

What is a metadata?

Metadata is the information about the data stored in datanodes such as location of the file, size of the file and so on.

What is a Datanode?

Datanodes are the slaves which are deployed on each machine and provide the actual storage. These are responsible for serving read and write requests for the clients.

Why do we use HDFS for applications having large data sets and not when there are lot of small files?

HDFS is more suitable for large amount of data sets in a single file as compared to small amount of data spread across multiple files. This is because Namenode is a very expensive high performance system, so it is not prudent to occupy the space in the Namenode by unnecessary amount of metadata that is generated for multiple small files. So, when there is a large amount of data in a single file, name node will occupy less space. Hence for getting optimized performance, HDFS supports large data sets instead of multiple small files.

What is a daemon?

Daemon is a process or service that runs in background. In general, we use this word in UNIX environment. The equivalent of Daemon in Windows is “services” and in Dos is ” TSR”.

What is a job tracker?

Job tracker is a daemon that runs on a namenode for submitting and tracking MapReduce jobs in Hadoop. It assigns the tasks to the different task tracker. In a Hadoop cluster, there will be only one job tracker but many task trackers. It is the single point of failure for Hadoop and MapReduce Service. If the job tracker goes down all the running jobs are halted. It receives heartbeat from task tracker based on which Job tracker decides whether the assigned task is completed or not.

What is a task tracker?

Task tracker is also a daemon that runs on datanodes. Task Trackers manage the execution of individual tasks on slave node. When a client submits a job, the job tracker will initialize the job and divide the work and assign them to different task trackers to perform MapReduce tasks. While performing this action, the task tracker will be simultaneously communicating with job tracker by sending heartbeat. If the job tracker does not receive heartbeat from task tracker within specified time, then it will assume that task tracker has crashed and assign that task to another task tracker in the cluster.

Is Namenode machine same as datanode machine as in terms of hardware?

It depends upon the cluster you are trying to create. The Hadoop VM can be there on the same machine or on another machine. For instance, in a single node cluster, there is only one machine, whereas in the development or in a testing environment, Namenode and datanodes are on different machines.

What is a ‘block’ in HDFS?

A ‘block’ is the minimum amount of data that can be read or written. In HDFS, the default block size is 64 MB as contrast to the block size of 8192 bytes in Unix/Linux. Files in HDFS are broken down into block-sized chunks, which are stored as independent units. HDFS blocks are large as compared to disk blocks, particularly to minimize the cost of seeks.
If a particular file is 50 mb, will the HDFS block still consume 64 mb as the default size?

No, not at all! 64 mb is just a unit where the data will be stored. In this particular situation, only 50 mb will be consumed by an HDFS block and 14 mb will be free to store something else. It is the MasterNode that does data allocation in an efficient manner.

What are the benefits of block transfer?

A file can be larger than any single disk in the network. There’s nothing that requires the blocks from a file to be stored on the same disk, so they can take advantage of any of the disks in the cluster. Making the unit of abstraction a block rather than a file simplifies the storage subsystem. Blocks provide fault tolerance and availability. To insure against corrupted blocks and disk and machine failure, each block is replicated to a small number of physically separate machines (typically three). If a block becomes unavailable, a copy can be read from another location in a way that is transparent to the client.

If we want to copy 10 blocks from one machine to another, but another machine can copy only 8.5 blocks, can the blocks be broken at the time of replication?

In HDFS, blocks cannot be broken down. Before copying the blocks from one machine to another, the Master node will figure out what is the actual amount of space required, how many block are being used, how much space is available, and it will allocate the blocks accordingly.

How indexing is done in HDFS?

Hadoop has its own way of indexing. Depending upon the block size, once the data is stored, HDFS will keep on storing the last part of the data which will say where the next part of the data will be. In fact, this is the base of HDFS.

If a data Node is full how it’s identified?

When data is stored in datanode, then the metadata of that data will be stored in the Namenode. So Namenode will identify if the data node is full.

If datanodes increase, then do we need to upgrade Namenode?

While installing the Hadoop system, Namenode is determined based on the size of the clusters. Most of the time, we do not need to upgrade the Namenode because it does not store the actual data, but just the metadata, so such a requirement rarely arise.

Are job tracker and task trackers present in separate machines?

Yes, job tracker and task tracker are present in different machines. The reason is job tracker is a single point of failure for the Hadoop MapReduce service. If it goes down, all running jobs are halted.

When we send a data to a node, do we allow settling in time, before sending another data to that node?

Yes, we do.

Does hadoop always require digital data to process?

Yes. Hadoop always require digital data to be processed.

On what basis Namenode will decide which datanode to write on?

As the Namenode has the metadata (information) related to all the data nodes, it knows which datanode is free.

Doesn’t Google have its very own version of DFS?

Yes, Google owns a DFS known as “Google File System (GFS)” developed by Google Inc. for its own use.

Who is a ‘user’ in HDFS?

A user is like you or me, who has some query or who needs some kind of data.

Is client the end user in HDFS?

No, Client is an application which runs on your machine, which is used to interact with the Namenode (job tracker) or datanode (task tracker).

What is the communication channel between client and namenode/datanode?

The mode of communication is SSH.

Is Hadoop replacing the role of OLAP (online analytical processing) in preparing data to answer specific questions?
No. Hadoop is powering unstructured ETL, queryable archiving, data-science exploratory sandboxing, and other use cases. OLAP–in terms of traditional cubing–remains key to front-end query acceleration in decision support applications and data marts. In support of those front-end applicatioins, OLAP is facing competition from other approaches, especially in-memory, columnar databases

What kind of expertise do you need to run a Big Data project in the enterprise?
Data-driven organizations succeed when all personnel—both technical and business—have a common understanding of the core big-data best skills, tools and practices. You need all the skills of data management, integration, modeling, and so forth that you already have running your data marts, warehouses, OLAP cubes.

What is a rack?

Rack is a storage area with all the datanodes put together. These datanodes can be physically located at different places. Rack is a physical collection of datanodes which are stored at a single location. There can be multiple racks in a single location.

On what basis data will be stored on a rack?

When the client is ready to load a file into the cluster, the content of the file will be divided into blocks. Now the client consults the Namenode and gets 3 datanodes for every block of the file which indicates where the block should be stored. While placing the datanodes, the key rule followed is “for every block of data, two copies will exist in one rack, third copy in a different rack“. This rule is known as “Replica Placement Policy“.

Do we need to place 2nd and 3rd data in rack 2 only?

Yes, this is to avoid datanode failure.

What if rack 2 and datanode fails?

If both rack2 and datanode present in rack 1 fails then there is no chance of getting data from it. In order to avoid such situations, we need to replicate that data more number of times instead of replicating only thrice. This can be done by changing the value in replication factor which is set to 3 by default.

What is a Secondary Namenode? Is it a substitute to the Namenode?

The secondary Namenode constantly reads the data from the RAM of the Namenode and writes it into the hard disk or the file system. It is not a substitute to the Namenode, so if the Namenode fails, the entire Hadoop system goes down.

What is the difference between Gen1 and Gen2 Hadoop with regards to the Namenode?

In Gen 1 Hadoop, Namenode is the single point of failure. In Gen 2 Hadoop, we have what is known as Active and Passive Namenodes kind of a structure. If the active Namenode fails, passive Namenode takes over the charge.

What is MapReduce?

Map Reduce is the ‘heart‘ of Hadoop that consists of two parts – ‘map’ and ‘reduce’. Maps and reduces are programs for processing data. ‘Map’ processes the data first to give some intermediate output which is further processed by ‘Reduce’ to generate the final output. Thus, MapReduce allows for distributed processing of the map and reduction operations.

Can you explain how do ‘map’ and ‘reduce’ work?

Namenode takes the input and divide it into parts and assign them to data nodes. These datanodes process the tasks assigned to them and make a key-value pair and returns the intermediate output to the Reducer. The reducer collects this key value pairs of all the datanodes and combines them and generates the final output.

What is ‘Key value pair’ in HDFS?

Key value pair is the intermediate data generated by maps and sent to reduces for generating the final output.

What is the difference between MapReduce engine and HDFS cluster?

HDFS cluster is the name given to the whole configuration of master and slaves where data is stored. Map Reduce Engine is the programming module which is used to retrieve and analyze data.

Is map like a pointer?

No, Map is not like a pointer.

Do we require two servers for the Namenode and the datanodes?

Yes, we need two different servers for the Namenode and the datanodes. This is because Namenode requires highly configurable system as it stores information about the location details of all the files stored in different datanodes and on the other hand, datanodes require low configuration system.

Why are the number of splits equal to the number of maps?

The number of maps is equal to the number of input splits because we want the key and value pairs of all the input splits.

Is a job split into maps?

No, a job is not split into maps. Spilt is created for the file. The file is placed on datanodes in blocks. For each split, a map is needed.

Which are the two types of ‘writes’ in HDFS?

There are two types of writes in HDFS: posted and non-posted write. Posted Write is when we write it and forget about it, without worrying about the acknowledgement. It is similar to our traditional Indian post. In a Non-posted Write, we wait for the acknowledgement. It is similar to the today’s courier services. Naturally, non-posted write is more expensive than the posted write. It is much more expensive, though both writes are asynchronous.

Why ‘Reading‘ is done in parallel and ‘Writing‘ is not in HDFS?

Reading is done in parallel because by doing so we can access the data fast. But we do not perform the write operation in parallel. The reason is that if we perform the write operation in parallel, then it might result in data inconsistency. For example, you have a file and two nodes are trying to write data into the file in parallel, then the first node does not know what the second node has written and vice-versa. So, this makes it confusing which data to be stored and accessed.

Does Pig give any warning when there is a type mismatch or missing field?

No, Pig will not show any warning if there is no matching field or a mismatch. If you assume that Pig gives such a warning, then it is difficult to find in log file. If any mismatch is found, it assumes a null value in Pig.

What co-group does in Pig?

Co-group joins the data set by grouping one particular data set only. It groups the elements by their common field and then returns a set of records containing two separate bags. The first bag consists of the record of the first data set with the common data set and the second bag consists of the records of the second data set with the common data set.

Can we say cogroup is a group of more than 1 data set?

Cogroup is a group of one data set. But in the case of more than one data sets, cogroup will group all the data sets and join them based on the common field. Hence, we can say that cogroup is a group of more than one data set and join of that data set as well.

What does FOREACH do?

FOREACH is used to apply transformations to the data and to generate new data items. The name itself is indicating that for each element of a data bag, the respective action will be performed.
Syntax : FOREACH bagname GENERATE expression1, expression2, …..
The meaning of this statement is that the expressions mentioned after GENERATE will be applied to the current record of the data bag.

What is bag?

A bag is one of the data models present in Pig. It is an unordered collection of tuples with possible duplicates. Bags are used to store collections while grouping. The size of bag is the size of the local disk, this means that the size of the bag is limited. When the bag is full, then Pig will spill this bag into local disk and keep only some parts of the bag in memory. There is no necessity that the complete bag should fit into memory. We represent bags with “{}”.
- See more at: http://www.edureka.in/blog/hadoop-interview-questions-pig/#sthash.GdvThrZH.dpuf

Can you give us some examples how Hadoop is used in real time environment?

Let us assume that the we have an exam consisting of 10 Multiple-choice questions and 20 students appear for that exam. Every student will attempt each question. For each question and each answer option, a key will be generated. So we have a set of key-value pairs for all the questions and all the answer options for every student. Based on the options that the students have selected, you have to analyze and find out how many students have answered correctly. This isn’t an easy task. Here Hadoop comes into picture! Hadoop helps you in solving these problems quickly and without much effort. You may also take the case of how many students have wrongly attempted a particular question.

What is BloomMapFile used for?

The BloomMapFile is a class that extends MapFile. So its functionality is similar to MapFile. BloomMapFile uses dynamic Bloom filters to provide quick membership test for the keys. It is used in Hbase table format.

What is PIG?

PIG is a platform for analyzing large data sets that consist of high level language for expressing data analysis programs, coupled with infrastructure for evaluating these programs. PIG’s infrastructure layer consists of a compiler that produces sequence of MapReduce Programs.

What is the difference between logical and physical plans?

Pig undergoes some steps when a Pig Latin Script is converted into MapReduce jobs. After performing the basic parsing and semantic checking, it produces a logical plan. The logical plan describes the logical operators that have to be executed by Pig during execution. After this, Pig produces a physical plan. The physical plan describes the physical operators that are needed to execute the script.

Does ‘ILLUSTRATE’ run MR job?

No, illustrate will not pull any MR, it will pull the internal data. On the console, illustrate will not do any job. It just shows output of each stage and not the final output.

Is the keyword ‘DEFINE’ like a function name?

Yes, the keyword ‘DEFINE’ is like a function name. Once you have registered, you have to define it. Whatever logic you have written in Java program, you have an exported jar and also a jar registered by you. Now the compiler will check the function in exported jar. When the function is not present in the library, it looks into your jar.

Is the keyword ‘FUNCTIONAL’ a User Defined Function (UDF)?

No, the keyword ‘FUNCTIONAL’ is not a User Defined Function (UDF). While using UDF, we have to override some functions. Certainly you have to do your job with the help of these functions only. But the keyword ‘FUNCTIONAL’ is a built-in function i.e a pre-defined function, therefore it does not work as a UDF.

Why do we need MapReduce during Pig programming?

Pig is a high-level platform that makes many Hadoop data analysis issues easier to execute. The language we use for this platform is: Pig Latin. A program written in Pig Latin is like a query written in SQL, where we need an execution engine to execute the query. So, when a program is written in Pig Latin, Pig compiler will convert the program into MapReduce jobs. Here, MapReduce acts as the execution engine.

Are there any problems which can only be solved by MapReduce and cannot be solved by PIG? In which kind of scenarios MR jobs will be more useful than PIG?

Let us take a scenario where we want to count the population in two cities. I have a data set and sensor list of different cities. I want to count the population by using one mapreduce for two cities. Let us assume that one is Bangalore and the other is Noida. So I need to consider key of Bangalore city similar to Noida through which I can bring the population data of these two cities to one reducer. The idea behind this is some how I have to instruct map reducer program – whenever you find city with the name ‘Bangalore‘ and city with the name ‘Noida’, you create the alias name which will be the common name for these two cities so that you create a common key for both the cities and it get passed to the same reducer. For this, we have to write custom partitioner.
In mapreduce when you create a ‘key’ for city, you have to consider ’city’ as the key. So, whenever the framework comes across a different city, it considers it as a different key. Hence, we need to use customized partitioner. There is a provision in mapreduce only, where you can write your custom partitioner and mention if city = bangalore or noida then pass similar hashcode. However, we cannot create custom partitioner in Pig. As Pig is not a framework, we cannot direct execution engine to customize the partitioner. In such scenarios, MapReduce works better than Pig.
- See more at: http://www.edureka.in/blog/hadoop-interview-questions-pig/#sthash.GdvThrZH.dpuf

Can you give us some examples how Hadoop is used in real time environment?

What is BloomMapFile used for?

What is PIG?

What is the difference between logical and physical plans?

Does ‘ILLUSTRATE’ run MR job?

No, illustrate will not pull any MR, it will pull the internal data. On the console, illustrate will not do any job. It just shows output of each stage and not the final output.

Is the keyword ‘DEFINE’ like a function name?

Is the keyword ‘FUNCTIONAL’ a User Defined Function (UDF)?

Why do we need MapReduce during Pig programming?

Are there any problems which can only be solved by MapReduce and cannot be solved by PIG? In which kind of scenarios MR jobs will be more useful than PIG?

Does Pig give any warning when there is a type mismatch or missing field?

What co-group does in Pig?

Can we say cogroup is a group of more than 1 data set?

What does FOREACH do?

What is bag?

What is MapReduce?

It is a framework or a programming model that is used for processing large data sets over clusters of computers using distributed programming.

What are ‘maps’ and ‘reduces’?

‘Maps‘ and ‘Reduces‘ are two phases of solving a query in HDFS. ‘Map’ is responsible to read data from input location, and based on the input type, it will generate a key value pair, that is, an intermediate output in local machine. ’Reducer’ is responsible to process the intermediate output received from the mapper and generate the final output.

What are the four basic parameters of a mapper?

The four basic parameters of a mapper are LongWritable, text, text and IntWritable. The first two represent input parameters and the second two represent intermediate output parameters.

What are the four basic parameters of a reducer?

The four basic parameters of a reducer are text, IntWritable, text, IntWritable. The first two represent intermediate output parameters and the second two represent final output parameters.

What do the master class and the output class do?

Master is defined to update the Master or the job tracker and the output class is defined to write data onto the output location.

What is the input type/format in MapReduce by default?

By default the type input type in MapReduce is ‘text’.

Is it mandatory to set input and output type/format in MapReduce?

No, it is not mandatory to set the input and output type/format in MapReduce. By default, the cluster takes the input and the output type as ‘text’.

What does the text input format do?

In text input format, each line will create a line object, that is an hexa-decimal number. Key is considered as a line object and value is considered as a whole line text. This is how the data gets processed by a mapper. The mapper will receive the ‘key’ as a ‘LongWritable‘ parameter and value as a ‘text‘ parameter.

What does job conf class do?

MapReduce needs to logically separate different jobs running on the same cluster. ‘Job conf class‘ helps to do job level settings such as declaring a job in real environment. It is recommended that Job name should be descriptive and represent the type of job that is being executed.

What does conf.setMapper Class do?

Conf.setMapper class sets the mapper class and all the stuff related to map job such as reading a data and generating a key-value pair out of the mapper.

What do sorting and shuffling do?

Sorting and shuffling are responsible for creating a unique key and a list of values. Making similar keys at one location is known as Sorting. And the process by which the intermediate output of the mapper is sorted and sent across to the reducers is known as Shuffling.

What does a split do?

Before transferring the data from hard disk location to map method, there is a phase or method called the ‘Split Method‘. Split method pulls a block of data from HDFS to the framework. The Split class does not write anything, but reads data from the block and pass it to the mapper. Be default, Split is taken care by the framework. Split method is equal to the block size and is used to divide block into bunch of splits.

How can we change the split size if our commodity hardware has less storage space?

If our commodity hardware has less storage space, we can change the split size by writing the ‘custom splitter‘. There is a feature of customization in Hadoop which can be called from the main method.

What does a MapReduce partitioner do?

A MapReduce partitioner makes sure that all the value of a single key goes to the same reducer, thus allows evenly distribution of the map output over the reducers. It redirects the mapper output to the reducer by determining which reducer is responsible for a particular key.

How is Hadoop different from other data processing tools?

In Hadoop, based upon your requirements, you can increase or decrease the number of mappers without bothering about the volume of data to be processed. this is the beauty of parallel processing in contrast to the other data processing tools available.

Can we rename the output file?

Yes we can rename the output file by implementing multiple format output class.

Why we cannot do aggregation (addition) in a mapper? Why we require reducer for that?

We cannot do aggregation (addition) in a mapper because, sorting is not done in a mapper. Sorting happens only on the reducer side. Mapper method initialization depends upon each input split. While doing aggregation, we will lose the value of the previous instance. For each row, a new mapper will get initialized. For each row, input split again gets divided into mapper, thus we do not have a track of the previous row value.

What is Streaming?

Streaming is a feature with Hadoop framework that allows us to do programming using MapReduce in any programming language which can accept standard input and can produce standard output. It could be Perl, Python, Ruby and not necessarily be Java. However, customization in MapReduce can only be done using Java and not any other programming language.

What is a Combiner?

A ‘Combiner’ is a mini reducer that performs the local reduce task. It receives the input from the mapper on a particular node and sends the output to the reducer. Combiners help in enhancing the efficiency of MapReduce by reducing the quantum of data that is required to be sent to the reducers.

What is the difference between an HDFS Block and Input Split?

HDFS Block is the physical division of the data and Input Split is the logical division of the data.

What happens in a textinputformat?

In textinputformat, each line in the text file is a record. Key is the byte offset of the line and value is the content of the line. For instance, Key: longWritable, value: text.

What do you know about keyvaluetextinputformat?

In keyvaluetextinputformat, each line in the text file is a ‘record‘. The first separator character divides each line. Everything before the separator is the key and everything after the separator is the value. For instance, Key: text, value: text.

What do you know about Sequencefileinputformat?

Sequencefileinputformat is an input format for reading in sequence files. Key and value are user defined. It is a specific compressed binary file format which is optimized for passing the data between the output of one MapReduce job to the input of some other MapReduce job.

ORACLE Interview Questions
What are the components of physical database structure of Oracle database?
Oracle database is comprised of three types of files. One or more datafiles, two are more redo log files, and one or more control files. What are the components of logical database structure of Oracle database?
There are tablespaces and database's schema objects.
What is a tablespace?
A database is divided into Logical Storage Unit called tablespaces. A tablespace is used to grouped related logical structures together.
What is SYSTEM tablespace and when is it created?
Every Oracle database contains a tablespace named SYSTEM, which is automatically created when the database is created. The SYSTEM tablespace always contains the data dictionary tables for the entire database.
Explain the relationship among database, tablespace and data file ?
Each databases logically divided into one or more tablespaces one or more data files are explicitly created for each tablespace.
What is schema?
A schema is collection of database objects of a user.
What are Schema Objects?
Schema objects are the logical structures that directly refer to the database's data. Schema objects include tables, views, sequences, synonyms, indexes, clusters, database triggers, procedures, functions packages and database links.
Can objects of the same schema reside in different tablespaces?
Yes.
Can a tablespace hold objects from different schemes?
Yes.
What is Oracle table?
A table is the basic unit of data storage in an Oracle database. The tables of a database hold all of the user accessible data. Table data is stored in rows and columns.
What is an Oracle view?
A view is a virtual table. Every view has a query attached to it. (The query is a SELECT statement that identifies the columns and rows of the table(s) the view uses.)
What is Partial Backup ?
A Partial Backup is any operating system backup short of a full backup, taken while the database is open or shut down.
What is Mirrored on-line Redo Log ?
A mirrored on-line redo log consists of copies of on-line redo log files physically located on separate disks, changes made to one member of the group are made to all members.
What is Full Backup ?
A full backup is an operating system backup of all data files, on-line redo log files and control file that constitute ORACLE database and the parameter.
Can a View based on another View ?
Yes.
Can a Tablespace hold objects from different Schemes ?
Yes.

Can objects of the same Schema reside in different tablespace ?
Yes.
What is the use of Control File ?
When an instance of an ORACLE database is started, its control file is used to identify the database and redo log files that must be opened for database operation to proceed. It is also used in database recovery.
Do View contain Data ?
Views do not contain or store data.
What are the Referential actions supported by FOREIGN KEY integrity constraint ?
UPDATE and DELETE Restrict - A referential integrity rule that disallows the update or deletion of referenced data. DELETE Cascade - When a referenced row is deleted all associated dependent rows are deleted.
What are the type of Synonyms?
There are two types of Synonyms Private and Public.
What is a Redo Log ?
The set of Redo Log files YSDATE,UID,USER or USERENV SQL functions, or the pseudo columns LEVEL or ROWNUM.
What is an Index Segment ?
Each Index has an Index segment that stores all of its data.

Explain the relationship among Database, Tablespace and Data file?
Each databases logically divided into one or more tablespaces one or more data files are explicitly created for each tablespace
What are the different type of Segments ?
Data Segment, Index Segment, Rollback Segment and Temporary Segment.
What are Clusters ?
Clusters are groups of one or more tables physically stores together to share common columns and are often used together.
What is an Integrity Constrains ?
An integrity constraint is a declarative way to define a business rule for a column of a table.
What is an Index ?
An Index is an optional structure associated with a table to have direct access to rows, which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.
What is an Extent ?
An Extent is a specific number of contiguous data blocks, obtained in a single allocation, and used to store a specific type of information.
What is a View ?
A view is a virtual table. Every view has a Query attached to it. (The Query is a SELECT statement that identifies the columns and rows of the table(s) the view uses.)
What is Table ?
A table is the basic unit of data storage in an ORACLE database. The tables of a database hold all of the user accessible data. Table data is stored in rows and columns.
Can a view based on another view?
Yes. What are the advantages of views?
- Provide an additional level of table security, by restricting access to a predetermined set of rows and columns of a table.
- Hide data complexity.
- Simplify commands for the user.
- Present the data in a different perspective from that of the base table.
- Store complex queries.
What is an Oracle sequence?
A sequence generates a serial list of unique numbers for numerical columns of a database's tables.
What is a synonym?
A synonym is an alias for a table, view, sequence or program unit.
What are the types of synonyms?
There are two types of synonyms private and public.
What is a private synonym?
Only its owner can access a private synonym.
What is a public synonym?
Any database user can access a public synonym.
What are synonyms used for?
- Mask the real name and owner of an object.
- Provide public access to an object
- Provide location transparency for tables, views or program units of a remote database.
- Simplify the SQL statements for database users.
What is an Oracle index?
An index is an optional structure associated with a table to have direct access to rows, which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.
How are the index updates?
Indexes are automatically maintained and used by Oracle. Changes to table data are automatically incorporated into all relevant indexes.
What is a Tablespace?
A database is divided into Logical Storage Unit called tablespace. A tablespace is used to grouped related logical structures together
What is Rollback Segment ?
A Database contains one or more Rollback Segments to temporarily store "undo" information.
What are the Characteristics of Data Files ?
A data file can be associated with only one database. Once created a data file can't change size. One or more data files form a logical unit of database storage called a tablespace.
How to define Data Block size ?
A data block size is specified for each ORACLE database when the database is created. A database users and allocated free database space in ORACLE data blocks. Block size is specified in INIT.ORA file and can't be changed latter.
What does a Control file Contain ?
A Control file records the physical structure of the database. It contains the following information.
Database Name
Names and locations of a database's files and redolog files.
Time stamp of database creation.
What is difference between UNIQUE constraint and PRIMARY KEY constraint ?
A column defined as UNIQUE can contain Nulls while a column defined as PRIMARY KEY can't contain Nulls.
What is Index Cluster ?
A Cluster with an index on the Cluster Key
When does a Transaction end ?
When it is committed or Rollbacked.
What is the effect of setting the value "ALL_ROWS" for OPTIMIZER_GOAL parameter of the ALTER SESSION command ? What are the factors that affect OPTIMIZER in choosing an Optimization approach ?
Answer The OPTIMIZER_MODE initialization parameter Statistics in the Data Dictionary the OPTIMIZER_GOAL parameter of the ALTER SESSION command hints in the statement.
What is the effect of setting the value "CHOOSE" for OPTIMIZER_GOAL, parameter of the ALTER SESSION Command ?
The Optimizer chooses Cost_based approach and optimizes with the goal of best throughput if statistics for atleast one of the tables accessed by the SQL statement exist in the data dictionary. Otherwise the OPTIMIZER chooses RULE_based approach.
How does one create a new database? (for DBA)
One can create and modify Oracle databases using the Oracle "dbca" (Database Configuration Assistant) utility. The dbca utility is located in the $ORACLE_HOME/bin directory. The Oracle Universal Installer (oui) normally starts it after installing the database server software.
One can also create databases manually using scripts. This option, however, is falling out of fashion, as it is quite involved and error prone. Look at this example for creating and Oracle 9i database:
CONNECT SYS AS SYSDBA
ALTER SYSTEM SET DB_CREATE_FILE_DEST='/u01/oradata/';
ALTER SYSTEM SET DB_CREATE_ONLINE_LOG_DEST_1='/u02/oradata/';
ALTER SYSTEM SET DB_CREATE_ONLINE_LOG_DEST_2='/u03/oradata/';
CREATE DATABASE;
What database block size should I use? (for DBA)
Oracle recommends that your database block size match, or be multiples of your operating system block size. One can use smaller block sizes, but the performance cost is significant. Your choice should depend on the type of application you are running. If you have many small transactions as with OLTP, use a smaller block size. With fewer but larger transactions, as with a DSS application, use a larger block size. If you are using a volume manager, consider your "operating system block size" to be 8K. This is because volume manager products use 8K blocks (and this is not configurable).
What are the different approaches used by Optimizer in choosing an execution plan ?
Rule-based and Cost-based.
What does ROLLBACK do ?
ROLLBACK retracts any of the changes resulting from the SQL statements in the transaction.
How does one coalesce free space ? (for DBA)
SMON coalesces free space (extents) into larger, contiguous extents every 2 hours and even then, only for a short period of time.
SMON will not coalesce free space if a tablespace's default storage parameter "pctincrease" is set to 0. With Oracle 7.3 one can manually coalesce a tablespace using the ALTER TABLESPACE ... COALESCE; command, until then use:
SQL> alter session set events 'immediate trace name coalesce level n';
Where 'n' is the tablespace number you get from SELECT TS#, NAME FROM SYS.TS$;
You can get status information about this process by selecting from the SYS.DBA_FREE_SPACE_COALESCED dictionary view.
How does one prevent tablespace fragmentation? (for DBA)
Always set PCTINCREASE to 0 or 100.
Bizarre values for PCTINCREASE will contribute to fragmentation. For example if you set PCTINCREASE to 1 you will see that your extents are going to have weird and wacky sizes: 100K, 100K, 101K, 102K, etc. Such extents of bizarre size are rarely re-used in their entirety. PCTINCREASE of 0 or 100 gives you nice round extent sizes that can easily be reused. E.g.. 100K, 100K, 200K, 400K, etc.

Use the same extent size for all the segments in a given tablespace. Locally Managed tablespaces (available from 8i onwards) with uniform extent sizes virtually eliminates any tablespace fragmentation. Note that the number of extents per segment does not cause any performance issue anymore, unless they run into thousands and thousands where additional I/O may be required to fetch the additional blocks where extent maps of the segment are stored.
Where can one find the high water mark for a table? (for DBA)
There is no single system table, which contains the high water mark (HWM) for a table. A table's HWM can be calculated using the results from the following SQL statements:
SELECT BLOCKS
FROM DBA_SEGMENTS
WHERE OWNER=UPPER(owner) AND SEGMENT_NAME = UPPER(table);
ANALYZE TABLE owner.table ESTIMATE STATISTICS;
SELECT EMPTY_BLOCKS
FROM DBA_TABLES
WHERE OWNER=UPPER(owner) AND SEGMENT_NAME = UPPER(table);
Thus, the tables' HWM = (query result 1) - (query result 2) - 1
NOTE: You can also use the DBMS_SPACE package and calculate the HWM = TOTAL_BLOCKS - UNUSED_BLOCKS - 1.
What is COST-based approach to optimization ?
Considering available access paths and determining the most efficient execution plan based on statistics in the data dictionary for the tables accessed by the statement and their associated clusters and indexes.
What does COMMIT do ?
COMMIT makes permanent the changes resulting from all SQL statements in the transaction. The changes made by the SQL statements of a transaction become visible to other user sessions transactions that start only after transaction is committed.
How are extents allocated to a segment? (for DBA)
Oracle8 and above rounds off extents to a multiple of 5 blocks when more than 5 blocks are requested. If one requests 16K or 2 blocks (assuming a 8K block size), Oracle doesn't round it up to 5 blocks, but it allocates 2 blocks or 16K as requested. If one asks for 8 blocks, Oracle will round it up to 10 blocks.
Space allocation also depends upon the size of contiguous free space available. If one asks for 8 blocks and Oracle finds a contiguous free space that is exactly 8 blocks, it would give it you. If it were 9 blocks, Oracle would also give it to you. Clearly Oracle doesn't always round extents to a multiple of 5 blocks.
The exception to this rule is locally managed tablespaces. If a tablespace is created with local extent management and the extent size is 64K, then Oracle allocates 64K or 8 blocks assuming 8K-block size. Oracle doesn't round it up to the multiple of 5 when a tablespace is locally managed.
Can one rename a database user (schema)? (for DBA)
No, this is listed as Enhancement Request 158508. Workaround:
Do a user-level export of user A
create new user B
Import system/manager fromuser=A touser=B
Drop user A

Define Transaction ?
A Transaction is a logical unit of work that comprises one or more SQL statements executed by a single user. What is Read-Only Transaction ?
A Read-Only transaction ensures that the results of each query executed in the transaction are consistant with respect to the same point in time.
What is a deadlock ? Explain .
Two processes wating to update the rows of a table which are locked by the other process then deadlock arises. In a database environment this will often happen because of not issuing proper row lock commands. Poor design of front-end application may cause this situation and the performance of server will reduce drastically.
These locks will be released automatically when a commit/rollback operation performed or any one of this processes being killed externally.
What is a Schema ?
The set of objects owned by user account is called the schema.
What is a cluster Key ?
The related columns of the tables are called the cluster key. The cluster key is indexed using a cluster index and its value is stored only once for multiple tables in the cluster.
What is Parallel Server ?
Multiple instances accessing the same database (Only In Multi-CPU environments)

What are the basic element of Base configuration of an oracle Database ?
It consists of
one or more data files.
one or more control files.
two or more redo log files.
The Database contains
multiple users/schemas
one or more rollback segments
one or more tablespaces
Data dictionary tables
User objects (table,indexes,views etc.,)
The server that access the database consists of
SGA (Database buffer, Dictionary Cache Buffers, Redo log buffers, Shared SQL pool)
SMON (System MONito)
PMON (Process MONitor)
LGWR (LoG Write)
DBWR (Data Base Write)
ARCH (ARCHiver)
CKPT (Check Point)
RECO
Dispatcher
User Process with associated PGS
What is clusters ?
Group of tables physically stored together because they share common columns and are often used together is called Cluster.
What is an Index ? How it is implemented in Oracle Database ?
An index is a database structure used by the server to have direct access of a row in a table. An index is automatically created when a unique of primary key constraint clause is specified in create table comman (Ver 7.0)
What is a Database instance ? Explain
A database instance (Server) is a set of memory structure and background processes that access a set of database files.
The process can be shared by all users. The memory structure that are used to store most queried data from database. This helps up to improve database performance by decreasing the amount of I/O performed against data file.
What is the use of ANALYZE command ?
To perform one of these function on an index, table, or cluster:
- To collect statistics about object used by the optimizer and store them in the data dictionary.
- To delete statistics about the object used by object from the data dictionary.
- To validate the structure of the object.
- To identify migrated and chained rows of the table or cluster.
What is default tablespace ?
The Tablespace to contain schema objects created without specifying a tablespace name.
What are the system resources that can be controlled through Profile ?
The number of concurrent sessions the user can establish the CPU processing time available to the user's session the CPU processing time available to a single call to ORACLE made by a SQL statement the amount of logical I/O available to the user's session the amout of logical I/O available to a single call to ORACLE made by a SQL statement the allowed amount of idle time for the user's session the allowed amount of connect time for the user's session.
What is Tablespace Quota ?
The collective amount of disk space available to the objects in a schema on a particular tablespace.
What are the different Levels of Auditing ?
Statement Auditing, Privilege Auditing and Object Auditing.
What is Statement Auditing ?
Statement auditing is the auditing of the powerful system privileges without regard to specifically named objects.
What are the database administrators utilities available ?
SQL * DBA - This allows DBA to monitor and control an ORACLE database. SQL * Loader - It loads data from standard operating system files (Flat files) into ORACLE database tables. Export (EXP) and Import (imp) utilities allow you to move existing data in ORACLE format to and from ORACLE database.
How can you enable automatic archiving ?
Shut the database
Backup the database
Modify/Include LOG_ARCHIVE_START_TRUE in init.ora file.
Start up the database.
What are roles? How can we implement roles ?
Roles are the easiest way to grant and manage common privileges needed by different groups of database users. Creating roles and assigning provides to roles. Assign each role to group of users. This will simplify the job of assigning privileges to individual users.
What are Roles ?
Roles are named groups of related privileges that are granted to users or other roles.

What are the use of Roles ?
REDUCED GRANTING OF PRIVILEGES - Rather than explicitly granting the same set of privileges to many users a database administrator can grant the privileges for a group of related users granted to a role and then grant only the role to each member of the group.
DYNAMIC PRIVILEGE MANAGEMENT - When the privileges of a group must change, only the privileges of the role need to be modified. The security domains of all users granted the group's role automatically reflect the changes made to the role.
SELECTIVE AVAILABILITY OF PRIVILEGES - The roles granted to a user can be selectively enable (available for use) or disabled (not available for use). This allows specific control of a user's privileges in any given situation.
APPLICATION AWARENESS - A database application can be designed to automatically enable and disable selective roles when a user attempts to use the application.
What is Privilege Auditing ?
Privilege auditing is the auditing of the use of powerful system privileges without regard to specifically named objects.
What is Object Auditing ?
Object auditing is the auditing of accesses to specific schema objects without regard to user.
What is Auditing ?
Monitoring of user access to aid in the investigation of database use.

How does one see the uptime for a database? (for DBA )
Look at the following SQL query:
SELECT to_char (startup_time,'DD-MON-YYYY HH24: MI: SS') "DB Startup Time"
FROM sys.v_$instance;
Marco Bergman provided the following alternative solution:
SELECT to_char (logon_time,'Dy dd Mon HH24: MI: SS') "DB Startup Time"
FROM sys.v_$session
WHERE Sid=1 /* this is pmon */
/
Users still running on Oracle 7 can try one of the following queries:
Column STARTED format a18 head 'STARTUP TIME'
Select C.INSTANCE,
to_date (JUL.VALUE, 'J')
|| to_char (floor (SEC.VALUE/3600), '09')
|| ':'
-- || Substr (to_char (mod (SEC.VALUE/60, 60), '09'), 2, 2)
|| Substr (to_char (floor (mod (SEC.VALUE/60, 60)), '09'), 2, 2)
|| '.'
|| Substr (to_char (mod (SEC.VALUE, 60), '09'), 2, 2) STARTED
from SYS.V_$INSTANCE JUL,
SYS.V_$INSTANCE SEC,
SYS.V_$THREAD C
Where JUL.KEY like '%JULIAN%'
and SEC.KEY like '%SECOND%';
Select to_date (JUL.VALUE, 'J')
|| to_char (to_date (SEC.VALUE, 'SSSSS'), ' HH24:MI:SS') STARTED
from SYS.V_$INSTANCE JUL,
SYS.V_$INSTANCE SEC
where JUL.KEY like '%JULIAN%'
and SEC.KEY like '%SECOND%';
select to_char (to_date (JUL.VALUE, 'J') + (SEC.VALUE/86400), -Return a DATE
'DD-MON-YY HH24:MI:SS') STARTED
from V$INSTANCE JUL,
V$INSTANCE SEC
where JUL.KEY like '%JULIAN%'
and SEC.KEY like '%SECOND%'; Where are my TEMPFILES, I don't see them in V$DATAFILE or DBA_DATA_FILE? (for DBA )
Tempfiles, unlike normal datafiles, are not listed in v$datafile or dba_data_files. Instead query v$tempfile or dba_temp_files:
SELECT * FROM v$tempfile;
SELECT * FROM dba_temp_files;

How do I find used/free space in a TEMPORARY tablespace? (for DBA )
Unlike normal tablespaces, true temporary tablespace information is not listed in DBA_FREE_SPACE. Instead use the V$TEMP_SPACE_HEADER view:
SELECT tablespace_name, SUM (bytes used), SUM (bytes free)
FROM V$temp_space_header
GROUP BY tablespace_name;
What is a profile ?
Each database user is assigned a Profile that specifies limitations on various system resources available to the user.
How will you enforce security using stored procedures?
Don't grant user access directly to tables within the application. Instead grant the ability to access the procedures that access the tables. When procedure executed it will execute the privilege of procedures owner. Users cannot access tables except via the procedure.
How can one see who is using a temporary segment? (for DBA )
For every user using temporary space, there is an entry in SYS.V$_LOCK with type 'TS'.
All temporary segments are named 'ffff.bbbb' where 'ffff' is the file it is in and 'bbbb' is first block of the segment. If your temporary tablespace is set to TEMPORARY, all sorts are done in one large temporary segment. For usage stats, see SYS.V_$SORT_SEGMENT
From Oracle 8.0, one can just query SYS.v$sort_usage. Look at these examples:
select s.username, u."USER", u.tablespace, u.contents, u.extents, u.blocks
from sys.v_$session s, sys.v_$sort_usage u
where s.addr = u.session_addr
/
select s.osuser, s.process, s.username, s.serial#,
Sum (u.blocks)*vp.value/1024 sort_size
from sys.v_$session s, sys.v_$sort_usage u, sys.v_$parameter VP
where s.saddr = u.session_addr
and vp.name = 'db_block_size'
and s.osuser like '&1'
group by s.osuser, s.process, s.username, s.serial#, vp.value
/
How does one get the view definition of fixed views/tables?
Query v$fixed_view_definition. Example: SELECT * FROM v$fixed_view_definition WHERE view_name='V$SESSION';
What are the dictionary tables used to monitor a database spaces ?
DBA_FREE_SPACE
DBA_SEGMENTS
DBA_DATA_FILES.
How can we specify the Archived log file name format and destination?
By setting the following values in init.ora file. LOG_ARCHIVE_FORMAT = arch %S/s/T/tarc (%S - Log sequence number and is zero left paded, %s - Log sequence number not padded. %T - Thread number lef-zero-paded and %t - Thread number not padded). The file name created is arch 0001 are if %S is used. LOG_ARCHIVE_DEST = path.
What is user Account in Oracle database?
An user account is not a physical structure in Database but it is having important relationship to the objects in the database and will be having certain privileges.
When will the data in the snapshot log be used?
We must be able to create a after row trigger on table (i.e., it should be not be already available) After giving table privileges. We cannot specify snapshot log name because oracle uses the name of the master table in the name of the database objects that support its snapshot log. The master table name should be less than or equal to 23 characters. (The table name created will be MLOGS_tablename, and trigger name will be TLOGS name).
What dynamic data replication?
Updating or Inserting records in remote database through database triggers. It may fail if remote database is having any problem.
What is Two-Phase Commit ?
Two-phase commit is mechanism that guarantees a distributed transaction either commits on all involved nodes or rolls back on all involved nodes to maintain data consistency across the global distributed database. It has two phase, a Prepare Phase and a Commit Phase.
How can you Enforce Referential Integrity in snapshots ?
Time the references to occur when master tables are not in use. Peform the reference the manually immdiately locking the master tables. We can join tables in snopshots by creating a complex snapshots that will based on the master tables.
What is a SQL * NET?
SQL *NET is ORACLE's mechanism for interfacing with the communication protocols used by the networks that facilitate distributed processing and distributed databases. It is used in Clint-Server and Server-Server communications.
What is a SNAPSHOT ?
Snapshots are read-only copies of a master table located on a remote node which is periodically refreshed to reflect changes made to the master table.
What is the mechanism provided by ORACLE for table replication ?
Snapshots and SNAPSHOT LOGs
What is snapshots?
Snapshot is an object used to dynamically replicate data between distribute database at specified time intervals. In ver 7.0 they are read only.
What are the various type of snapshots?
Simple and Complex.
Describe two phases of Two-phase commit ?
Prepare phase - The global coordinator (initiating node) ask a participants to prepare (to promise to commit or rollback the transaction, even if there is a failure) Commit - Phase - If all participants respond to the coordinator that they are prepared, the coordinator asks all nodes to commit the transaction, if all participants cannot prepare, the coordinator asks all nodes to roll back the transaction.
What is snapshot log ?
It is a table that maintains a record of modifications to the master table in a snapshot. It is stored in the same database as master table and is only available for simple snapshots. It should be created before creating snapshots.
What are the benefits of distributed options in databases?
Database on other servers can be updated and those transactions can be grouped together with others in a logical unit.
Database uses a two phase commit.
What are the options available to refresh snapshots ?
COMPLETE - Tables are completely regenerated using the snapshots query and the master tables every time the snapshot referenced.
FAST - If simple snapshot used then a snapshot log can be used to send the changes to the snapshot tables.
FORCE - Default value. If possible it performs a FAST refresh; Otherwise it will perform a complete refresh.
What is a SNAPSHOT LOG ?
A snapshot log is a table in the master database that is associated with the master table. ORACLE uses a snapshot log to track the rows that have been updated in the master table. Snapshot logs are used in updating the snapshots based on the master table.
What is Distributed database ?
A distributed database is a network of databases managed by multiple database servers that appears to a user as single logical database. The data of all databases in the distributed database can be simultaneously accessed and modified.
How can we reduce the network traffic?
- Replication of data in distributed environment.
- Using snapshots to replicate data.
- Using remote procedure calls.
Differentiate simple and complex, snapshots ?
- A simple snapshot is based on a query that does not contains GROUP BY clauses, CONNECT BY clauses, JOINs, sub-query or snashot of operations.
- A complex snapshots contain atleast any one of the above.
What are the Built-ins used for sending Parameters to forms?
You can pass parameter values to a form when an application executes the call_form, New_form, Open_form or Run_product.
Can you have more than one content canvas view attached with a window?
Yes. Each window you create must have atleast one content canvas view assigned to it. You can also create a window that has manipulated content canvas view. At run time only one of the content canvas views assign to a window is displayed at a time.
Is the After report trigger fired if the report execution fails?
Yes.
Does a Before form trigger fire when the parameter form is suppressed?
Yes.

What is SGA?
The System Global Area in an Oracle database is the area in memory to facilitate the transfer of information between users. It holds the most recently requested structural information between users. It holds the most recently requested structural information about the database. The structure is database buffers, dictionary cache, redo log buffer and shared pool area. What is a shared pool?
The data dictionary cache is stored in an area in SGA called the shared pool. This will allow sharing of parsed SQL statements among concurrent users.
What is mean by Program Global Area (PGA)?
It is area in memory that is used by a single Oracle user process.
What is a data segment?
Data segment are the physical areas within a database block in which the data associated with tables and clusters are stored.
What are the factors causing the reparsing of SQL statements in SGA?
Due to insufficient shared pool size.
Monitor the ratio of the reloads takes place while executing SQL statements. If the ratio is greater than 1 then increase the SHARED_POOL_SIZE.
What are clusters?
Clusters are groups of one or more tables physically stores together to share common columns and are often used together.
What is cluster key?
The related columns of the tables in a cluster are called the cluster key.
Do a view contain data?
Views do not contain or store data.
What is user Account in Oracle database?
A user account is not a physical structure in database but it is having important relationship to the objects in the database and will be having certain privileges.
How will you enforce security using stored procedures?
Don't grant user access directly to tables within the application. Instead grant the ability to access the procedures that access the tables. When procedure executed it will execute the privilege of procedures owner. Users cannot access tables except via the procedure.
What are the dictionary tables used to monitor a database space?
DBA_FREE_SPACE
DBA_SEGMENTS
DBA_DATA_FILES.
Can a property clause itself be based on a property clause?
Yes
If a parameter is used in a query without being previously defined, what diff. exist between. report 2.0 and 2.5 when the query is applied?
While both reports 2.0 and 2.5 create the parameter, report 2.5 gives a message that a bind parameter has been created.
What are the sql clauses supported in the link property sheet?
Where start with having.
What is trigger associated with the timer?
When-timer-expired.
What are the trigger associated with image items?
When-image-activated fires when the operators double clicks on an image itemwhen-image-pressed fires when an operator clicks or double clicks on an image item
What are the different windows events activated at runtimes?
When_window_activated
When_window_closed
When_window_deactivated
When_window_resized
Within this triggers, you can examine the built in system variable system. event_window to determine the name of the window for which the trigger fired.
When do you use data parameter type?
When the value of a data parameter being passed to a called product is always the name of the record group defined in the current form. Data parameters are used to pass data to products invoked with the run_product built-in subprogram.
What is difference between open_form and call_form?
when one form invokes another form by executing open_form the first form remains displayed, and operators can navigate between the forms as desired. when one form invokes another form by executing call_form, the called form is modal with respect to the calling form. That is, any windows that belong to the calling form are disabled, and operators cannot navigate to them until they first exit the called form.
What is new_form built-in?
When one form invokes another form by executing new_form oracle form exits the first form and releases its memory before loading the new form calling new form completely replace the first with the second. If there are changes pending in the first form, the operator will be prompted to save them before the new form is loaded.
What is the "LOV of Validation" Property of an item? What is the use of it?
When LOV for Validation is set to True, Oracle Forms compares the current value of the text item to the values in the first column displayed in the LOV. Whenever the validation event occurs. If the value in the text item matches one of the values in the first column of the LOV, validation succeeds, the LOV is not displayed, and processing continues normally. If the value in the text item does not match one of the values in the first column of the LOV, Oracle Forms displays the LOV and uses the text item value as the search criteria to automatically reduce the list.
What is the diff. when Flex mode is mode on and when it is off?
When flex mode is on, reports automatically resizes the parent when the child is resized.
What is the diff. when confine mode is on and when it is off?
When confine mode is on, an object cannot be moved outside its parent in the layout.
What are visual attributes?
Visual attributes are the font, color, pattern proprieties that you set for form and menu objects that appear in your application interface.
Which of the two views should objects according to possession?
view by structure.
What are the two types of views available in the object navigator(specific to report 2.5)?
View by structure and view by type .
What are the vbx controls?
Vbx control provide a simple method of building and enhancing user interfaces. The controls can use to obtain user inputs and display program outputs.vbx control where originally develop as extensions for the ms visual basic environments and include such items as sliders, rides and knobs.
What is the use of transactional triggers?
Using transactional triggers we can control or modify the default functionality of the oracle forms.
How do you create a new session while open a new form?
Using open_form built-in setting the session option Ex. Open_form('Stocks ',active, session). when invoke the multiple forms with open form and call_form in the same application, state whether the following are true/False
What are the ways to monitor the performance of the report?
Use reports profile executable statement. Use SQL trace facility.
If two groups are not linked in the data model editor, What is the hierarchy between them?
Two group that is above are the left most rank higher than the group that is to right or below it.
An open form can not be execute the call_form procedure if you chain of called forms has been initiated by another open form?
True
Explain about horizontal, Vertical tool bar canvas views?
Tool bar canvas views are used to create tool bars for individual windows. Horizontal tool bars are display at the top of a window, just under its menu bar. Vertical Tool bars are displayed along the left side of a window
What is the purpose of the product order option in the column property sheet?
To specify the order of individual group evaluation in a cross products.
What is the use of image_zoom built-in?
To manipulate images in image items.
How do you reference a parameter indirectly?
To indirectly reference a parameter use the NAME IN, COPY 'built-ins to indirectly set and reference the parameters value' Example name_in ('capital parameter my param'), Copy ('SURESH','Parameter my_param')
What is a timer?
Timer is an "internal time clock" that you can programmatically create to perform an action each time the times.
What are the two phases of block coordination?
There are two phases of block coordination: the clear phase and the population phase. During, the clear phase, Oracle Forms navigates internally to the detail block and flushes the obsolete detail records. During the population phase, Oracle Forms issues a SELECT statement to repopulate the detail block with detail records associated with the new master record. These operations are accomplished through the execution of triggers.
What are Most Common types of Complex master-detail relationships?
There are three most common types of complex master-detail relationships:
master with dependent details
master with independent details
detail with two masters

What is a text list?
The text list style list item appears as a rectangular box which displays the fixed number of values. When the text list contains values that can not be displayed, a vertical scroll bar appears, allowing the operator to view and select undisplayed values.
What is term?
The term is terminal definition file that describes the terminal form which you are using r20run.
What is use of term?
The term file which key is correspond to which oracle report functions.
What is pop list?
The pop list style list item appears initially as a single field (similar to a text item field). When the operator selects the list icon, a list of available choices appears.
What is the maximum no of chars the parameter can store?
The maximum no of chars the parameter can store is only valid for char parameters, which can be upto 64K. No parameters default to 23Bytes and Date parameter default to 7Bytes.
What are the default extensions of the files created by library module?
The default file extensions indicate the library module type and storage format .pll - pl/sql library module binary
What are the Coordination Properties in a Master-Detail relationship?
The coordination properties are
Deferred
Auto-Query
These Properties determine when the population phase of block
coordination should occur.
How do you display console on a window ?
The console includes the status line and message line, and is displayed at the bottom of the window to which it is assigned.To specify that the console should be displayed, set the console window form property to the name of any window in the form. To include the console, set console window to Null.
What are the different Parameter types?
Text ParametersData Parameters
State any three mouse events system variables?
System.mouse_button_pressedSystem.mouse_button_shift
What are the types of calculated columns available?
Summary, Formula, Placeholder column.
Explain about stacked canvas views?
Stacked canvas view is displayed in a window on top of, or "stacked" on the content canvas view assigned to that same window. Stacked canvas views obscure some part of the underlying content canvas view, and or often shown and hidden programmatically.
How does one do off-line database backups? (for DBA )
Shut down the database from sqlplus or server manager. Backup all files to secondary storage (eg. tapes). Ensure that you backup all data files, all control files and all log files. When completed, restart your database.
Do the following queries to get a list of all files that needs to be backed up:
select name from sys.v_$datafile;
select member from sys.v_$logfile;
select name from sys.v_$controlfile;
Sometimes Oracle takes forever to shutdown with the "immediate" option. As workaround to this problem, shutdown using these commands:
alter system checkpoint;
shutdown abort
startup restrict
shutdown immediate
Note that if you database is in ARCHIVELOG mode, one can still use archived log files to roll forward from an off-line backup. If you cannot take your database down for a cold (off-line) backup at a convenient time, switch your database into ARCHIVELOG mode and perform hot (on-line) backups.
What is the difference between SHOW_EDITOR and EDIT_TEXTITEM?
Show editor is the generic built-in which accepts any editor name and takes some input string and returns modified output string. Whereas the edit_textitem built-in needs the input focus to be in the text item before the built-in is executed.
What are the built-ins that are used to Attach an LOV programmatically to an item?
set_item_property
get_item_property
(by setting the LOV_NAME property)
How does one do on-line database backups? (for DBA )
Each tablespace that needs to be backed-up must be switched into backup mode before copying the files out to secondary storage (tapes). Look at this simple example.
ALTER TABLESPACE xyz BEGIN BACKUP;
! cp xyfFile1 /backupDir/
ALTER TABLESPACE xyz END BACKUP;
It is better to backup tablespace for tablespace than to put all tablespaces in backup mode. Backing them up separately incurs less overhead. When done, remember to backup your control files. Look at this example:
ALTER SYSTEM SWITCH LOGFILE; -- Force log switch to update control file headers
ALTER DATABASE BACKUP CONTROLFILE TO '/backupDir/control.dbf';
NOTE: Do not run on-line backups during peak processing periods. Oracle will write complete database blocks instead of the normal deltas to redo log files while in backup mode. This will lead to excessive database archiving and even database freezes.
How does one backup a database using RMAN? (for DBA )
The biggest advantage of RMAN is that it only backup used space in the database. Rman doesn't put tablespaces in backup mode, saving on redo generation overhead. RMAN will re-read database blocks until it gets a consistent image of it. Look at this simple backup example.
rman target sys/*** nocatalog
run {
allocate channel t1 type disk;
backup
format '/app/oracle/db_backup/%d_t%t_s%s_p%p'
( database );
release channel t1;
}
Example RMAN restore:
rman target sys/*** nocatalog
run {
allocate channel t1 type disk;
# set until time 'Aug 07 2000 :51';
restore tablespace users;
recover tablespace users;
release channel t1;
}
The examples above are extremely simplistic and only useful for illustrating basic concepts. By default Oracle uses the database controlfiles to store information about backups. Normally one would rather setup a RMAN catalog database to store RMAN metadata in. Read the Oracle Backup and Recovery Guide before implementing any RMAN backups.
Note: RMAN cannot write image copies directly to tape. One needs to use a third-party media manager that integrates with RMAN to backup directly to tape. Alternatively one can backup to disk and then manually copy the backups to tape.
What are the different file extensions that are created by oracle reports?
Rep file and Rdf file.
What is strip sources generate options?
Removes the source code from the library file and generates a library files that contains only pcode. The resulting file can be used for final deployment, but can not be subsequently edited in the designer.ex. f45gen module=old_lib.pll userid=scott/tiger strip_source YES output_file
How does one put a database into ARCHIVELOG mode? (for DBA )
The main reason for running in archivelog mode is that one can provide 24-hour availability and guarantee complete data recoverability. It is also necessary to enable ARCHIVELOG mode before one can start to use on-line database backups. To enable ARCHIVELOG mode, simply change your database startup command script, and bounce the database:
SQLPLUS> connect sys as sysdba
SQLPLUS> startup mount exclusive;
SQLPLUS> alter database archivelog;
SQLPLUS> archive log start;
SQLPLUS> alter database open;
NOTE1: Remember to take a baseline database backup right after enabling archivelog mode. Without it one would not be able to recover. Also, implement an archivelog backup to prevent the archive log directory from filling-up.
NOTE2: ARCHIVELOG mode was introduced with Oracle V6, and is essential for database point-in-time recovery. Archiving can be used in combination with on-line and off-line database backups.
NOTE3: You may want to set the following INIT.ORA parameters when enabling ARCHIVELOG mode: log_archive_start=TRUE, log_archive_dest=... and log_archive_format=...
NOTE4: You can change the archive log destination of a database on-line with the ARCHIVE LOG START TO 'directory'; statement. This statement is often used to switch archiving between a set of directories.
NOTE5: When running Oracle Real Application Server (RAC), you need to shut down all nodes before changing the database to ARCHIVELOG mode.
What is the basic data structure that is required for creating an LOV?
Record Group.
How does one backup archived log files? (for DBA )
One can backup archived log files using RMAN or any operating system backup utility. Remember to delete files after backing them up to prevent the archive log directory from filling up. If the archive log directory becomes full, your database will hang! Look at this simple RMAN backup script:
RMAN> run {
2> allocate channel dev1 type disk;
3> backup
4> format '/app/oracle/arch_backup/log_t%t_s%s_p%p'
5> (archivelog all delete input);
6> release channel dev1;
7> }
Does Oracle write to data files in begin/hot backup mode? (for DBA )
Oracle will stop updating file headers, but will continue to write data to the database files even if a tablespace is in backup mode.
In backup mode, Oracle will write out complete changed blocks to the redo log files. Normally only deltas (changes) are logged to the redo logs. This is done to enable reconstruction of a block if only half of it was backed up (split blocks). Because of this, one should notice increased log activity and archiving during on-line backups. What is the Maximum allowed length of Record group Column?
Record group column names cannot exceed 30 characters.
Which parameter can be used to set read level consistency across multiple queries?
Read only
What are the different types of Record Groups?
Query Record Groups
NonQuery Record Groups
State Record Groups
From which designation is it preferred to send the output to the printed?
Previewer

What are difference between post database commit and post-form commit?
Post-form commit fires once during the post and commit transactions process, after the database commit occurs. The post-form-commit trigger fires after inserts, updates and deletes have been posted to the database but before the transactions have been finalized in the issuing the command. The post-database-commit trigger fires after oracle forms issues the commit to finalized transactions.
What are the different display styles of list items?
Pop_listText_listCombo box
Which of the above methods is the faster method?
performing the calculation in the query is faster.
With which function of summary item is the compute at options required?
percentage of total functions.
What are parameters?
Parameters provide a simple mechanism for defining and setting the valuesof inputs that are required by a form at startup. Form parameters are variables of type char,number,date that you define at design time.
What are the three types of user exits available ?
Oracle Precompiler exits, Oracle call interface, NonOracle user exits.
How many windows in a form can have console?
Only one window in a form can display the console, and you cannot change the console assignment at runtime.
What is an administrative (privileged) user? (for DBA )
Oracle DBAs and operators typically use administrative accounts to manage the database and database instance. An administrative account is a user that is granted SYSOPER or SYSDBA privileges. SYSDBA and SYSOPER allow access to a database instance even if it is not running. Control of these privileges is managed outside of the database via password files and special operating system groups. This password file is created with the orapwd utility.
What are the two repeating frame always associated with matrix object?
One down repeating frame below one across repeating frame.
What are the master-detail triggers?
On-Check_delete_masterOn_clear_detailsOn_populate_details
How does one connect to an administrative user? (for DBA )
If an administrative user belongs to the "dba" group on Unix, or the "ORA_DBA" (ORA_sid_DBA) group on NT, he/she can connect like this:
connect / as sysdba
No password is required. This is equivalent to the desupported "connect internal" method.
A password is required for "non-secure" administrative access. These passwords are stored in password files. Remote connections via Net8 are classified as non-secure. Look at this example:
connect sys/password as sysdba
How does one create a password file? (for DBA )
The Oracle Password File ($ORACLE_HOME/dbs/orapw or orapwSID) stores passwords for users with administrative privileges. One needs to create a password files before remote administrators (like OEM) will be allowed to connect.
Follow this procedure to create a new password file:
. Log in as the Oracle software owner
. Runcommand: orapwd file=$ORACLE_HOME/dbs/orapw$ORACLE_SID password=mypasswd
. Shutdown the database (SQLPLUS> SHUTDOWN IMMEDIATE)
. Edit the INIT.ORA file and ensure REMOTE_LOGIN_PASSWORDFILE=exclusive is set.
. Startup the database (SQLPLUS> STARTUP)
NOTE: The orapwd utility presents a security risk in that it receives a password from the command line. This password is visible in the process table of many systems. Administrators needs to be aware of this!
Is it possible to modify an external query in a report which contains it?
No.
Does a grouping done for objects in the layout editor affect the grouping done in the data model editor?
No.
How does one add users to a password file? (for DBA )
One can select from the SYS.V_$PWFILE_USERS view to see which users are listed in the password file. New users can be added to the password file by granting them SYSDBA or SYSOPER privileges, or by using the orapwd utility. GRANT SYSDBA TO scott;
If a break order is set on a column would it affect columns which are under the column?
No
Why are OPS$ accounts a security risk in a client/server environment? (for DBA)
If you allow people to log in with OPS$ accounts from Windows Workstations, you cannot be sure who they really are. With terminals, you can rely on operating system passwords, with Windows, you cannot.
If you set REMOTE_OS_AUTHENT=TRUE in your init.ora file, Oracle assumes that the remote OS has authenticated the user. If REMOTE_OS_AUTHENT is set to FALSE (recommended), remote users will be unable to connect without a password. IDENTIFIED EXTERNALLY will only be in effect from the local host. Also, if you are using "OPS$" as your prefix, you will be able to log on locally with or without a password, regardless of whether you have identified your ID with a password or defined it to be IDENTIFIED EXTERNALLY.
Do user parameters appear in the data modal editor in 2.5?
No
Can you pass data parameters to forms?
No
Is it possible to link two groups inside a cross products after the cross products group has been created?
no
What are the different modals of windows?
Modalless windows
Modal windows
What are modal windows?
Modal windows are usually used as dialogs, and have restricted functionality compared to modelless windows. On some platforms for example operators cannot resize, scroll or iconify a modal window.
What are the different default triggers created when Master Deletes Property is set to Non-isolated?
Master Deletes Property Resulting Triggers
----------------------------------------------------
Non-Isolated(the default) On-Check-Delete-Master
On-Clear-Details
On-Populate-Details
What are the different default triggers created when Master Deletes Property is set to isolated?
Master Deletes Property Resulting Triggers
---------------------------------------------------
Isolated On-Clear-Details
On-Populate-Details
What are the different default triggers created when Master Deletes Property is set to Cascade?
Master Deletes Property Resulting Triggers
---------------------------------------------------
Cascading On-Clear-Details
On-Populate-Details
Pre-delete
What is the diff. bet. setting up of parameters in reports 2.0 reports2.5?
LOVs can be attached to parameters in the reports 2.5 parameter form.
What are the difference between lov & list item?
Lov is a property where as list item is an item. A list item can have only one column, lov can have one or more columns.
What is the advantage of the library?
Libraries provide a convenient means of storing client-side program units and sharing them among multiple applications. Once you create a library, you can attach it to any other form, menu, or library modules. When you can call library program units from triggers menu items commands and user named routine, you write in the modules to which you have attach the library. When a library attaches another library, program units in the first library can reference program units in the attached library. Library support dynamic loading-that is library program units are loaded into an application only when needed. This can significantly reduce the run-time memory requirements of applications.
What is lexical reference? How can it be created?
Lexical reference is place_holder for text that can be embedded in a sql statements. A lexical reference can be created using & before the column or parameter name.
What is system.coordination_operation?
It represents the coordination causing event that occur on the master block in master-detail relation.
What is synchronize?
It is a terminal screen with the internal state of the form. It updates the screen display to reflect the information that oracle forms has in its internal representation of the screen.
What use of command line parameter cmd file?
It is a command line argument that allows you to specify a file that contain a set of arguments for r20run.
What is a Text_io Package?
It allows you to read and write information to a file in the file system.
What is forms_DDL?
Issues dynamic Sql statements at run time, including server side pl/SQl and DDL
How is link tool operation different bet. reports 2 & 2.5?
In Reports 2.0 the link tool has to be selected and then two fields to be linked are selected and the link is automatically created. In 2.5 the first field is selected and the link tool is then used to link the first field to the second field.
What are the different styles of activation of ole Objects?
In place activationExternal activation
How do you reference a Parameter?
In Pl/Sql, You can reference and set the values of form parameters using bind variables syntax. Ex. PARAMETER name = '' or :block.item = PARAMETER Parameter name
What is the difference between object embedding & linking in Oracle forms?
In Oracle forms, Embedded objects become part of the form module, and linked objects are references from a form module to a linked source file.
Name of the functions used to get/set canvas properties?
Get_view_property, Set_view_property
What are the built-ins that are used for setting the LOV properties at runtime?
get_lov_property
set_lov_property

What are the built-ins used for processing rows?
Get_group_row_count(function)
Get_group_selection_count(function)
Get_group_selection(function)
Reset_group_selection(procedure)
Set_group_selection(procedure)
Unset_group_selection(procedure)
What are built-ins used for Processing rows?
GET_GROUP_ROW_COUNT(function)
GET_GROUP_SELECTION_COUNT(function)
GET_GROUP_SELECTION(function)
RESET_GROUP_SELECTION(procedure)
SET_GROUP_SELECTION(procedure)
UNSET_GROUP_SELECTION(procedure)
What are the built-in used for getting cell values?
Get_group_char_cell(function)
Get_groupcell(function)
Get_group_number_cell(function)
What are the built-ins used for Getting cell values?
GET_GROUP_CHAR_CELL (function)
GET_GROUPCELL(function)
GET_GROUP_NUMBET_CELL(function)
Atleast how many set of data must a data model have before a data model can be base on it?
Four
To execute row from being displayed that still use column in the row which property can be used?
Format trigger.
What are different types of modules available in oracle form?
Form module - a collection of objects and code routines Menu modules - a collection of menus and menu item commands that together make up an application menu library module - a collection of user named procedures, functions and packages that can be called from other modules in the application
What is the remove on exit property?
For a modelless window, it determines whether oracle forms hides the window automatically when the operators navigates to an item in the another window.
What is WHEN-Database-record trigger?
Fires when oracle forms first marks a record as an insert or an update. The trigger fires as soon as oracle forms determines through validation that the record should be processed by the next post or commit as an insert or update. c generally occurs only when the operators modifies the first item in the record, and after the operator attempts to navigate out of the item.
What is a difference between pre-select and pre-query?
Fires during the execute query and count query processing after oracle forms constructs the select statement to be issued, but before the statement is actually issued. The pre-query trigger fires just before oracle forms issues the select statement to the database after the operator as define the example records by entering the query criteria in enter query mode.Pre-query trigger fires before pre-select trigger.
What are built-ins associated with timers?
find_timercreate_timerdelete_timer
What are the built-ins used for finding object ID functions?
Find_group(function)
Find_column(function)
What are the built-ins used for finding Object ID function?
FIND_GROUP(function)
FIND_COLUMN(function)
Any attempt to navigate programmatically to disabled form in a call_form stack is allowed?
False
Use the Add_group_row procedure to add a row to a static record group 1. true or false?
False What third party tools can be used with Oracle EBU/ RMAN? (for DBA)
The following Media Management Software Vendors have integrated their media management software packages with Oracle Recovery Manager and Oracle7 Enterprise Backup Utility. The Media Management Vendors will provide first line technical support for the integrated backup/recover solutions.
Veritas NetBackup
EMC Data Manager (EDM)
HP OMNIBack II
IBM's Tivoli Storage Manager - formerly ADSM
Legato Networker
ManageIT Backup and Recovery
Sterling Software's SAMS:Alexandria - formerly from Spectralogic
Sun Solstice Backup
Why and when should one tune? (for DBA)
One of the biggest responsibilities of a DBA is to ensure that the Oracle database is tuned properly. The Oracle RDBMS is highly tunable and allows the database to be monitored and adjusted to increase its performance. One should do performance tuning for the following reasons:
The speed of computing might be wasting valuable human time (users waiting for response); Enable your system to keep-up with the speed business is conducted; and Optimize hardware usage to save money (companies are spending millions on hardware). Although this FAQ is not overly concerned with hardware issues, one needs to remember than you cannot tune a Buick into a Ferrari.
How can a break order be created on a column in an existing group? What are the various sub events a mouse double click event involves?
By dragging the column outside the group.
What is the use of place holder column? What are the various sub events a mouse double click event involves?
A placeholder column is used to hold calculated values at a specified place rather than allowing is to appear in the actual row where it has to appear.
What is the use of hidden column? What are the various sub events a mouse double click event involves?
A hidden column is used to when a column has to embed into boilerplate text.
What database aspects should be monitored? (for DBA)
One should implement a monitoring system to constantly monitor the following aspects of a database. Writing custom scripts, implementing Oracle's Enterprise Manager, or buying a third-party monitoring product can achieve this. If an alarm is triggered, the system should automatically notify the DBA (e-mail, page, etc.) to take appropriate action.
Infrastructure availability:
. Is the database up and responding to requests
. Are the listeners up and responding to requests
. Are the Oracle Names and LDAP Servers up and responding to requests
. Are the Web Listeners up and responding to requests

Things that can cause service outages:
. Is the archive log destination filling up?
. Objects getting close to their max extents
. User and process limits reached

Things that can cause bad performance:
See question "What tuning indicators can one use?".
Where should the tuning effort be directed? (for DBA)
Consider the following areas for tuning. The order in which steps are listed needs to be maintained to prevent tuning side effects. For example, it is no good increasing the buffer cache if you can reduce I/O by rewriting a SQL statement. Database Design (if it's not too late):
Poor system performance usually results from a poor database design. One should generally normalize to the 3NF. Selective denormalization can provide valuable performance improvements. When designing, always keep the "data access path" in mind. Also look at proper data partitioning, data replication, aggregation tables for decision support systems, etc.
Application Tuning:
Experience showed that approximately 80% of all Oracle system performance problems are resolved by coding optimal SQL. Also consider proper scheduling of batch tasks after peak working hours.
Memory Tuning:
Properly size your database buffers (shared pool, buffer cache, log buffer, etc) by looking at your buffer hit ratios. Pin large objects into memory to prevent frequent reloads.
Disk I/O Tuning:
Database files needs to be properly sized and placed to provide maximum disk subsystem throughput. Also look for frequent disk sorts, full table scans, missing indexes, row chaining, data fragmentation, etc
Eliminate Database Contention:
Study database locks, latches and wait events carefully and eliminate where possible. Tune the Operating System:
Monitor and tune operating system CPU, I/O and memory utilization. For more information, read the related Oracle FAQ dealing with your specific operating system.
What are the various sub events a mouse double click event involves? What are the various sub events a mouse double click event involves?
Double clicking the mouse consists of the mouse down, mouse up, mouse click, mouse down & mouse up events.

What are the default parameter that appear at run time in the parameter screen? What are the various sub events a mouse double click event involves?
Destype and Desname.
What are the built-ins used for Creating and deleting groups?
CREATE-GROUP (function)
CREATE_GROUP_FROM_QUERY(function)
DELETE_GROUP(procedure)
What are different types of canvas views?
Content canvas views
Stacked canvas views
Horizontal toolbar
vertical toolbar.
What are the different types of Delete details we can establish in Master-Details?
Cascade
Isolate
Non-isolate
What is relation between the window and canvas views?
Canvas views are the back ground objects on which you place the interface items (Text items), check boxes, radio groups etc.,) and boilerplate objects (boxes, lines, images etc.,) that operators interact with us they run your form . Each canvas views displayed in a window.
What is a User_exit?
Calls the user exit named in the user_exit_string. Invokes a 3Gl program by name which has been properly linked into your current oracle forms executable.
How is it possible to select generate a select set for the query in the query property sheet?
By using the tables/columns button and then specifying the table and the column names.
How can values be passed bet. precompiler exits & Oracle call interface?
By using the statement EXECIAFGET & EXECIAFPUT.
How can a square be drawn in the layout editor of the report writer?
By using the rectangle tool while pressing the (Constraint) key.

How can a text file be attached to a report while creating in the report writer?
By using the link file property in the layout boiler plate property sheet.
How can I message to passed to the user from reports?
By using SRW.MESSAGE function.
Does one need to drop/ truncate objects before importing? (for DBA)
Before one import rows into already populated tables, one needs to truncate or drop these tables to get rid of the old data. If not, the new data will be appended to the existing tables. One must always DROP existing Sequences before re-importing. If the sequences are not dropped, they will generate numbers inconsistent with the rest of the database. Note: It is also advisable to drop indexes before importing to speed up the import process. Indexes can easily be recreated after the data was successfully imported.
How can a button be used in a report to give a drill down facility?
By setting the action associated with button to Execute pl/sql option and using the SRW.Run_report function.
Can one import/export between different versions of Oracle? (for DBA)
Different versions of the import utility is upwards compatible. This means that one can take an export file created from an old export version, and import it using a later version of the import utility. This is quite an effective way of upgrading a database from one release of Oracle to the next.
Oracle also ships some previous catexpX.sql scripts that can be executed as user SYS enabling older imp/exp versions to work (for backwards compatibility). For example, one can run $ORACLE_HOME/rdbms/admin/catexp7.sql on an Oracle 8 database to allow the Oracle 7.3 exp/imp utilities to run against an Oracle 8 database.
What are different types of images?
Boiler plate imagesImage Items
Can one export to multiple files?/ Can one beat the Unix 2 Gig limit? (for DBA)
From Oracle8i, the export utility supports multiple output files. This feature enables large exports to be divided into files whose sizes will not exceed any operating system limits (FILESIZE= parameter). When importing from multi-file export you must provide the same filenames in the same sequence in the FILE= parameter. Look at this example:
exp SCOTT/TIGER FILE=D:\F1.dmp,E:\F2.dmp FILESIZE=10m LOG=scott.log
Use the following technique if you use an Oracle version prior to 8i:
Create a compressed export on the fly. Depending on the type of data, you probably can export up to 10 gigabytes to a single file. This example uses gzip. It offers the best compression I know of, but you can also substitute it with zip, compress or whatever.
# create a named pipe
mknod exp.pipe p
# read the pipe - output to zip file in the background
gzip < exp.pipe > scott.exp.gz &
# feed the pipe
exp userid=scott/tiger file=exp.pipe ...
What is bind reference and how can it be created?
Bind reference are used to replace the single value in sql, pl/sql statements a bind reference can be created using a (:) before a column or a parameter name.
How can one improve Import/ Export performance? (for DBA)
EXPORT:

. Set the BUFFER parameter to a high value (e.g. 2M)
. Set the RECORDLENGTH parameter to a high value (e.g. 64K)
. Stop unnecessary applications to free-up resources for your job.
. If you run multiple export sessions, ensure they write to different physical disks.
. DO NOT export to an NFS mounted filesystem. It will take forever.
IMPORT:

. Create an indexfile so that you can create indexes AFTER you have imported data. Do this by setting INDEXFILE to a filename and then import. No data will be imported but a file containing index definitions will be created. You must edit this file afterwards and supply the passwords for the schemas on all CONNECT statements.
. Place the file to be imported on a separate physical disk from the oracle data files
. Increase DB_CACHE_SIZE (DB_BLOCK_BUFFERS prior to 9i) considerably in the init$SID.ora file
. Set the LOG_BUFFER to a big value and restart oracle.
. Stop redo log archiving if it is running (ALTER DATABASE NOARCHIVELOG;)
. Create a BIG tablespace with a BIG rollback segment inside. Set all other rollback segments offline (except the SYSTEM rollback segment of course). The rollback segment must be as big as your biggest table (I think?)
. Use COMMIT=N in the import parameter file if you can afford it
. Use ANALYZE=N in the import parameter file to avoid time consuming ANALYZE statements
. Remember to run the indexfile previously created
Give the sequence of execution of the various report triggers?
Before form , After form , Before report, Between page, After report.
What are the common Import/ Export problems? (for DBA )
ORA-00001: Unique constraint (...) violated - You are importing duplicate rows. Use IGNORE=NO to skip tables that already exist (imp will give an error if the object is re-created).
ORA-01555: Snapshot too old - Ask your users to STOP working while you are exporting or use parameter CONSISTENT=NO
ORA-01562: Failed to extend rollback segment - Create bigger rollback segments or set parameter COMMIT=Y while importing
IMP-00015: Statement failed ... object already exists... - Use the IGNORE=Y import parameter to ignore these errors, but be careful as you might end up with duplicate rows.
Why is it preferable to create a fewer no. of queries in the data model?
Because for each query, report has to open a separate cursor and has to rebind, execute and fetch data.
Where is the external query executed at the client or the server?
At the server.
Where is a procedure return in an external pl/sql library executed at the client or at the server?
At the client.
What is coordination Event?
Any event that makes a different record in the master block the current record is a coordination causing event.
What is the difference between OLE Server & Ole Container?
An Ole server application creates ole Objects that are embedded or linked in ole Containers ex. Ole servers are ms_word & ms_excel. OLE containers provide a place to store, display and manipulate objects that are created by ole server applications. Ex. oracle forms is an example of an ole Container.
What is an object group?
An object group is a container for a group of objects; you define an object group when you want to package related objects, so that you copy or reference them in other modules.
What is an LOV?
An LOV is a scrollable popup window that provides the operator with either a single or multi column selection list.
At what point of report execution is the before Report trigger fired?
After the query is executed but before the report is executed and the records are displayed.
What are the built -ins used for Modifying a groups structure?
ADD-GROUP_COLUMN (function)
ADD_GROUP_ROW (procedure)
DELETE_GROUP_ROW(procedure)

What is an user exit used for?
A way in which to pass control (and possibly arguments ) form Oracle report to another Oracle products of 3 GL and then return control ( and ) back to Oracle reports.
What is the User-Named Editor?
A user named editor has the same text editing functionality as the default editor, but, because it is a named object, you can specify editor attributes such as windows display size, position, and title.
My database was terminated while in BACKUP MODE, do I need to recover? (for DBA)
If a database was terminated while one of its tablespaces was in BACKUP MODE (ALTER TABLESPACE xyz BEGIN BACKUP;), it will tell you that media recovery is required when you try to restart the database. The DBA is then required to recover the database and apply all archived logs to the database. However, from Oracle7.2, you can simply take the individual datafiles out of backup mode and restart the database.
ALTER DATABASE DATAFILE '/path/filename' END BACKUP;
One can select from V$BACKUP to see which datafiles are in backup mode. This normally saves a significant amount of database down time.
Thiru Vadivelu contributed the following:
From Oracle9i onwards, the following command can be used to take all of the datafiles out of hot backup mode:
ALTER DATABASE END BACKUP;
The above commands need to be issued when the database is mounted.
What is a Static Record Group?
A static record group is not associated with a query, rather, you define its structure and row values at design time, and they remain fixed at runtime.
What is a record group?
A record group is an internal Oracle Forms that structure that has a column/row framework similar to a database table. However, unlike database tables, record groups are separate objects that belong to the form module which they are defined.
My database is down and I cannot restore. What now? (for DBA )
Recovery without any backup is normally not supported, however, Oracle Consulting can sometimes extract data from an offline database using a utility called DUL (Disk UnLoad). This utility reads data in the data files and unloads it into SQL*Loader or export dump files. DUL does not care about rollback segments, corrupted blocks, etc, and can thus not guarantee that the data is not logically corrupt. It is intended as an absolute last resort and will most likely cost your company a lot of money!!!
I've lost my REDOLOG files, how can I get my DB back? (for DBA)
The following INIT.ORA parameter may be required if your current redo logs are corrupted or blown away. Caution is advised when enabling this parameter as you might end-up losing your entire database. Please contact Oracle Support before using it. _allow_resetlogs_corruption = true
What is a property clause?
A property clause is a named object that contains a list of properties and their settings. Once you create a property clause you can base other object on it. An object based on a property can inherit the setting of any property in the clause that makes sense for that object.

What is a physical page ? & What is a logical page ?
A physical page is a size of a page. That is output by the printer. The logical page is the size of one page of the actual report as seen in the Previewer.
I've lost some Rollback Segments, how can I get my DB back? (for DBA)
Re-start your database with the following INIT.ORA parameter if one of your rollback segments is corrupted. You can then drop the corrupted rollback segments and create it from scratch.
Caution is advised when enabling this parameter, as uncommitted transactions will be marked as committed. One can very well end up with lost or inconsistent data!!! Please contact Oracle Support before using it. _Corrupted_rollback_segments = (rbs01, rbs01, rbs03, rbs04)
What are the differences between EBU and RMAN? (for DBA)
Enterprise Backup Utility (EBU) is a functionally rich, high performance interface for backing up Oracle7 databases. It is sometimes referred to as OEBU for Oracle Enterprise Backup Utility. The Oracle Recovery Manager (RMAN) utility that ships with Oracle8 and above is similar to Oracle7's EBU utility. However, there is no direct upgrade path from EBU to RMAN.
How does one create a RMAN recovery catalog? (for DBA)
Start by creating a database schema (usually called rman). Assign an appropriate tablespace to it and grant it the recovery_catalog_owner role. Look at this example:
sqlplus sys
SQL>create user rman identified by rman;
SQL> alter user rman default tablespace tools temporary tablespace temp;
SQL> alter user rman quota unlimited on tools;
SQL> grant connect, resource, recovery_catalog_owner to rman;
SQL> exit;
Next, log in to rman and create the catalog schema. Prior to Oracle 8i this was done by running the catrman.sql script. rman catalog rman/rman
RMAN>create catalog tablespace tools;
RMAN> exit;
You can now continue by registering your databases in the catalog. Look at this example:
rman catalog rman/rman target backdba/backdba
RMAN> register database;
How can a group in a cross products be visually distinguished from a group that does not form a cross product?
A group that forms part of a cross product will have a thicker border.
What is the frame & repeating frame?
A frame is a holder for a group of fields. A repeating frame is used to display a set of records when the no. of records that are to displayed is not known before.
What is a combo box?
A combo box style list item combines the features found in list and text item. Unlike the pop list or the text list style list items, the combo box style list item will both display fixed values and accept one operator entered value.
What are three panes that appear in the run time pl/sql interpreter?
1. Source pane.
2. interpreter pane.
3. Navigator pane.

What are the two panes that Appear in the design time pl/sql interpreter?
1. Source pane.
2. Interpreter pane
What are the two ways by which data can be generated for a parameters list of values?
1. Using static values.
2. Writing select statement.

What are the various methods of performing a calculation in a report ?
1. Perform the calculation in the SQL statements itself.
2. Use a calculated / summary column in the data model.
What are the default extensions of the files created by menu module?
.mmb,
.mmx
What are the default extensions of the files created by forms modules?
.fmb - form module binary
.fmx - form module executable
To display the page no. for each page on a report what would be the source & logical page no. or & of physical page no.?
& physical page no.
It is possible to use raw devices as data files and what is the advantages over file. system files ?
Yes. The advantages over file system files. I/O will be improved because Oracle is bye-passing the kernnel which writing into disk. Disk Corruption will be very less.
What are disadvantages of having raw devices ?
We should depend on export/import utility for backup/recovery (fully reliable) The tar command cannot be used for physical file backup, instead we can use dd command which is less flexible and has limited recoveries.
What is the significance of having storage clause ?
We can plan the storage for a table as how much initial extents are required, how much can be extended next, how much % should leave free for managing row updations etc.,
What is the use of INCTYPE option in EXP command ?
Type export should be performed COMPLETE,CUMULATIVE,INCREMENTAL. List the sequence of events when a large transaction that exceeds beyond its optimal value when an entry wraps and causes the rollback segment toexpand into anotion Completes. e. will be written.

What is the use of FILE option in IMP command ?
The name of the file from which import should be performed.
What is a Shared SQL pool?
The data dictionary cache is stored in an area in SGA called the Shared SQL Pool. This will allow sharing of parsed SQL statements among concurrent users.
What is hot backup and how it can be taken?
Taking backup of archive log files when database is open. For this the ARCHIVELOG mode should be enabled. The following files need to be backed up. All data files. All Archive log, redo log files. All control files.
List the Optional Flexible Architecture (OFA) of Oracle database? or How can we organize the tablespaces in Oracle database to have maximum performance ?
SYSTEM - Data dictionary tables.
DATA - Standard operational tables.
DATA2- Static tables used for standard operations
INDEXES - Indexes for Standard operational tables.
INDEXES1 - Indexes of static tables used for standard operations.
TOOLS - Tools table.
TOOLS1 - Indexes for tools table.
RBS - Standard Operations Rollback Segments,
RBS1,RBS2 - Additional/Special Rollback segments.
TEMP - Temporary purpose tablespace
TEMP_USER - Temporary tablespace for users.
USERS - User tablespace.
How to implement the multiple control files for an existing database ?
Shutdown the database Copy one of the existing control file to new location Edit Config ora file by adding new control file. name Restart the database.
What is advantage of having disk shadowing/ Mirroring ?
Shadow set of disks save as a backup in the event of disk failure. In most Operating System if any disk failure occurs it automatically switchover to place of failed disk. Improved performance because most OS support volume shadowing can direct file I/O request to use the shadow set of files instead of the main set of files. This reduces I/O load on the main set of disks.
How will you force database to use particular rollback segment ?
SET TRANSACTION USE ROLLBACK SEGMENT rbs_name.
Why query fails sometimes ?
Rollback segment dynamically extent to handle larger transactions entry loads. A single transaction may wipeout all available free space in the Rollback Segment Tablespace. This prevents other user using Rollback segments.
What is the use of RECORD LENGTH option in EXP command ?
Record length in bytes.
How will you monitor rollback segment status ?
Querying the DBA_ROLLBACK_SEGS view
IN USE - Rollback Segment is on-line.
AVAILABLE - Rollback Segment available but not on-line.
OFF-LINE - Rollback Segment off-line
INVALID - Rollback Segment Dropped.
NEEDS RECOVERY - Contains data but need recovery or corupted.
PARTLY AVAILABLE - Contains data from an unresolved transaction involving a distributed database.
What is meant by Redo Log file mirroring ? How it can be achieved?
Process of having a copy of redo log files is called mirroring. This can be achieved by creating group of log files together, so that LGWR will automatically writes them to all the members of the current on-line redo log group. If any one group fails then database automatically switch over to next group. It degrades performance.
Which parameter in Storage clause will reduce no. of rows per block?
PCTFREE parameter
Row size also reduces no of rows per block.
What is meant by recursive hints ?
Number of times processes repeatedly query the dictionary table is called recursive hints. It is due to the data dictionary cache is too small. By increasing the SHARED_POOL_SIZE parameter we can optimize the size of Data Dictionary Cache.
What is the use of PARFILE option in EXP command ?
Name of the parameter file to be passed for export.
What is the difference between locks, latches, enqueues and semaphores? (for DBA)
A latch is an internal Oracle mechanism used to protect data structures in the SGA from simultaneous access. Atomic hardware instructions like TEST-AND-SET is used to implement latches. Latches are more restrictive than locks in that they are always exclusive. Latches are never queued, but will spin or sleep until they obtain a resource, or time out.
Enqueues and locks are different names for the same thing. Both support queuing and concurrency. They are queued and serviced in a first-in-first-out (FIFO) order.
Semaphores are an operating system facility used to control waiting. Semaphores are controlled by the following Unix parameters: semmni, semmns and semmsl. Typical settings are:
semmns = sum of the "processes" parameter for each instance
(see init<instance>.ora for each instance)
semmni = number of instances running simultaneously;
semmsl = semmns
What is a logical backup?
Logical backup involves reading a set of database records and writing them into a file. Export utility is used for taking backup and Import utility is used to recover from backup.
Where can one get a list of all hidden Oracle parameters? (for DBA)
Oracle initialization or INIT.ORA parameters with an underscore in front are hidden or unsupported parameters. One can get a list of all hidden parameters by executing this query:
select *
from SYS.X$KSPPI
where substr(KSPPINM,1,1) = '_';
The following query displays parameter names with their current value:
select a.ksppinm "Parameter", b.ksppstvl "Session Value", c.ksppstvl "Instance Value"
from x$ksppi a, x$ksppcv b, x$ksppsv c
where a.indx = b.indx and a.indx = c.indx
and substr(ksppinm,1,1)='_'
order by a.ksppinm;
Remember: Thou shall not play with undocumented parameters!
What is a database EVENT and how does one set it? (for DBA)
Oracle trace events are useful for debugging the Oracle database server. The following two examples are simply to demonstrate syntax. Refer to later notes on this page for an explanation of what these particular events do.
Either adding them to the INIT.ORA parameter file can activate events. E.g.
event='1401 trace name errorstack, level 12'
... or, by issuing an ALTER SESSION SET EVENTS command: E.g.
alter session set events '10046 trace name context forever, level 4';
The alter session method only affects the user's current session, whereas changes to the INIT.ORA file will affect all sessions once the database has been restarted.
What is a Rollback segment entry ?
It is the set of before image data blocks that contain rows that are modified by a transaction. Each Rollback Segment entry must be completed within one rollback segment. A single rollback segment can have multiple rollback segment entries.

What database events can be set? (for DBA)
The following events are frequently used by DBAs and Oracle Support to diagnose problems:
" 10046 trace name context forever, level 4 Trace SQL statements and show bind variables in trace output.
" 10046 trace name context forever, level 8 This shows wait events in the SQL trace files
" 10046 trace name context forever, level 12 This shows both bind variable names and wait events in the SQL trace files
" 1401 trace name errorstack, level 12 1401 trace name errorstack, level 4 1401 trace name processstate Dumps out trace information if an ORA-1401 "inserted value too large for column" error occurs. The 1401 can be replaced by any other Oracle Server error code that you want to trace.
" 60 trace name errorstack level 10 Show where in the code Oracle gets a deadlock (ORA-60), and may help to diagnose the problem.
The following lists of events are examples only. They might be version specific, so please call Oracle before using them:
" 10210 trace name context forever, level 10 10211 trace name context forever, level 10 10231 trace name context forever, level 10 These events prevent database block corruptions
" 10049 trace name context forever, level 2 Memory protect cursor
" 10210 trace name context forever, level 2 Data block check
" 10211 trace name context forever, level 2 Index block check
" 10235 trace name context forever, level 1 Memory heap check
" 10262 trace name context forever, level 300 Allow 300 bytes memory leak for connections
Note: You can use the Unix oerr command to get the description of an event. On Unix, you can type "oerr ora 10053" from the command prompt to get event details.

How can one dump internal database structures? (for DBA)
The following (mostly undocumented) commands can be used to obtain information about internal database structures.
o Dump control file contents
alter session set events 'immediate trace name CONTROLF level 10'
/
o Dump file headers
alter session set events 'immediate trace name FILE_HDRS level 10'
/
o Dump redo log headers
alter session set events 'immediate trace name REDOHDR level 10'
/
o Dump the system state
NOTE: Take 3 successive SYSTEMSTATE dumps, with 10-minute intervals alter session set events 'immediate trace name SYSTEMSTATE level 10'
/
o Dump the process state
alter session set events 'immediate trace name PROCESSSTATE level 10'
/
o Dump Library Cache details
alter session set events 'immediate trace name library cache level 10'
/
o Dump optimizer statistics whenever a SQL statement is parsed (hint: change statement or flush pool) alter session set events '10053 trace name context forever, level 1'
/
o Dump a database block (File/ Block must be converted to DBA address) Convert file and block number to a DBA (database block address).
Eg: variable x varchar2;
exec :x := dbms_utility.make_data_block_address(1,12);
print x
alter session set events 'immediate trace name blockdump level 50360894'
/
What are the different kind of export backups?
Full back - Complete database
Incremental - Only affected tables from last incremental date/full backup date.
Cumulative backup - Only affected table from the last cumulative date/full backup date.
How free extents are managed in Ver 6.0 and Ver 7.0 ?
Free extents cannot be merged together in Ver 6.0.
Free extents are periodically coalesces with the neighboring free extent in Ver 7.0
What is the use of RECORD option in EXP command?
For Incremental exports, the flag indirects whether a record will be stores data dictionary tables recording the export.
What is the use of ROWS option in EXP command ?
Flag to indicate whether table rows should be exported. If 'N' only DDL statements for the database objects will be created.
What is the use of COMPRESS option in EXP command ?
Flag to indicate whether export should compress fragmented segments into single extents.
How will you swap objects into a different table space for an existing database ?
Export the user
Perform import using the command imp system/manager file=export.dmp indexfile=newrite.sql.
This will create all definitions into newfile.sql. Drop necessary objects.
Run the script newfile.sql after altering the tablespaces.
Import from the backup for the necessary objects.
How does Space allocation table place within a block ?
Each block contains entries as follows
Fixed block header
Variable block header
Row Header,row date (multiple rows may exists)
PCTEREE (% of free space for row updation in future)
What are the factors causing the reparsing of SQL statements in SGA?
Due to insufficient Shared SQL pool size. Monitor the ratio of the reloads takes place while executing SQL statements. If the ratio is greater than 1 then increase the SHARED_POOL_SIZE. LOGICAL & PHYSICAL ARCHITECTURE OF DATABASE.
What is dictionary cache ?
Dictionary cache is information about the databse objects stored in a data dictionary table.
What is a Control file ?
Database overall physical architecture is maintained in a file called control file. It will be used to maintain internal consistency and guide recovery operations. Multiple copies of control files are advisable.
What is Database Buffers ?
Database buffers are cache in the SGA used to hold the data blocks that are read from the data segments in the database such as tables, indexes and clusters DB_BLOCK_BUFFERS parameter in INIT.ORA decides the size.
How will you create multiple rollback segments in a database ?
Create a database which implicitly creates a SYSTEM Rollback Segment in a SYSTEM tablespace. Create a Second Rollback Segment name R0 in the SYSTEM tablespace. Make new rollback segment available (After shutdown, modify init.ora file and Start database) Create other tablespaces (RBS) for rollback segments. Deactivate Rollback Segment R0 and activate the newly created rollback segments.
What is cold backup? What are the elements of it?
Cold backup is taking backup of all physical files after normal shutdown of database. We need to take.
- All Data files.
- All Control files.
- All on-line redo log files.
- The init.ora file (Optional)
What is meant by redo log buffer ?
Changes made to entries are written to the on-line redo log files. So that they can be used in roll forward operations during database recoveries. Before writing them into the redo log files, they will first brought to redo log buffers in SGA and LGWR will write into files frequently. LOG_BUFFER parameter will decide the size.
How will you estimate the space required by a non-clustered tables?
Calculate the total header size
Calculate the available dataspace per data block
Calculate the combined column lengths of the average row
Calculate the total average row size.
Calculate the average number rows that can fit in a block
Calculate the number of blocks and bytes required for the table.
After arriving the calculation, add 10 % additional space to calculate the initial extent size for a working table.
How will you monitor the space allocation ?
By querying DBA_SEGMENT table/view.
What is meant by free extent ?
A free extent is a collection of continuous free blocks in tablespace. When a segment is dropped its extents are reallocated and are marked as free.
What is the use of IGNORE option in IMP command ?
A flag to indicate whether the import should ignore errors encounter when issuing CREATE commands.
What is the use of ANALYSE ( Ver 7) option in EXP command ?
A flag to indicate whether statistical information about the exported objects should be written to export dump file.
What is the use of ROWS option in IMP command ?
A flag to indicate whether rows should be imported. If this is set to 'N' then only DDL for database objects will be executed.
What is the use of INDEXES option in EXP command ?
A flag to indicate whether indexes on tables will be exported.
What is the use of INDEXES option in IMP command ?
A flag to indicate whether import should import index on tables or not.
What is the use of GRANT option in EXP command?
A flag to indicate whether grants on databse objects will be exported or not. Value is 'Y' or 'N'.
What is the use of GRANT option in IMP command ?
A flag to indicate whether grants on database objects will be imported.
What is the use of FULL option in EXP command ?
A flag to indicate whether full databse export should be performed.
What is the use of SHOW option in IMP command ?
A flag to indicate whether file content should be displayed or not.
What is the use of CONSTRAINTS option in EXP command ?
A flag to indicate whether constraints on table need to be exported.
What is the use of CONSISTENT (Ver 7) option in EXP command ?
A flag to indicate whether a read consistent version of all the exported objects should be maintained.
What are the different methods of backing up oracle database ?
- Logical Backups
- Cold Backups
- Hot Backups (Archive log)
What is the difference between ON-VALIDATE-FIELD trigger and a POST-CHANGE trigger ?
When you changes the Existing value to null, the On-validate field trigger will fire post change trigger will not fire. At the time of execute-query post-change trigger will fire, on-validate field trigger will not fire.
When is PRE-QUERY trigger executed ?
When Execute-query or count-query Package procedures are invoked.

How do you trap the error in forms 3.0 ?
using On-Message or On-Error triggers.
How many pages you can in a single form ?
Unlimited
While specifying master/detail relationship between two blocks specifying the join condition is a must ?
True or False. ?
True
EXIT_FORM is a restricted package procedure ?
a. True b. False
True

What is the usage of an ON-INSERT,ON-DELETE and ON-UPDATE TRIGGERS ?
These triggers are executes when inserting, deleting and updating operations are performed and can be used to change the default function of insert, delete or update respectively. For Eg, instead of inserting a row in a table an existing row can be updated in the same table.
What are the types of Pop-up window ?
the pop-up field editor
pop-up list of values
pop-up pages.
Alert :
What is an SQL *FORMS ?
SQL *forms is 4GL tool for developing and executing; Oracle based interactive application.
How do you control the constraints in forms ?
Select the use constraint property is ON Block definition screen.
BLOCK
What is the difference between restricted and unrestricted package procedure ?
Restricted package procedure that affects the basic functions of SQL * Forms. It cannot used in all triggers except key triggers. Unrestricted package procedure that does not interfere with the basic functions of SQL * Forms it can be used in any triggers.
A query fetched 10 records How many times does a PRE-QUERY Trigger and POST-QUERY Trigger will get executed ?
PRE-QUERY fires once.
POST-QUERY fires 10 times.
Give the sequence in which triggers fired during insert operations, when the following 3 triggers are defined at the same block level ?
a. ON-INSERT b. POST-INSERT c. PRE-INSERT
State the order in which these triggers are executed ?
POST-FIELD,ON-VALIDATE-FIELD,POST-CHANGE and KEY-NEXTFLD. KEY-NEXTFLD,POST-CHANGE, ON-VALIDATE-FIELD, POST-FIELD. g.
What the PAUSE package procedure does ?
Pause suspends processing until the operator presses a function key
What do you mean by a page ?
Pages are collection of display information, such as constant text and graphics
What are the type of User Exits ?
ORACLE Precompliers user exits
OCI (ORACLE Call Interface)
Non-ORACEL user exits.
Page :
What is the difference between an ON-VALIDATE-FIELD trigger and a trigger ?
On-validate-field trigger fires, when the field Validation status New or changed. Post-field-trigger whenever the control leaving form the field, it will fire.
Can we use a restricted package procedure in ON-VALIDATE-FIELD Trigger ?
No
Is a Key startup trigger fires as result of a operator pressing a key explicitly ?
No
Can we use GO-BLOCK package in a pre-field trigger ?
No
Can we create two blocks with the same name in form 3.0 ?
No
What does an on-clear-block Trigger fire?
It fires just before SQL * forms the current block.
Name the two files that are created when you generate the form give the filex extension ?
INP (Source File)
FRM (Executable File)
What package procedure used for invoke sql *plus from sql *forms ?
Host (E.g. Host (sqlplus))
What is the significance of PAGE 0 in forms 3.0 ?
Hide the fields for internal calculation.
What are the different types of key triggers ?
Function Key
Key-function
Key-others
Key-startup
What is the difference between a Function Key Trigger and Key Function Trigger ?
Function key triggers are associated with individual SQL*FORMS function keys You can attach Key function triggers to 10 keys or key sequences that normally do not perform any SQL * FORMS operations. These keys referred as key F0 through key F9.
Committed block sometimes refer to a BASE TABLE ?
False
Error_Code is a package proecdure ?
a. True b. false
False
When is cost based optimization triggered? (for DBA)
It's important to have statistics on all tables for the CBO (Cost Based Optimizer) to work correctly. If one table involved in a statement does not have statistics, Oracle has to revert to rule-based optimization for that statement. So you really want for all tables to have statistics right away; it won't help much to just have the larger tables analyzed.
Generally, the CBO can change the execution plan when you:
1. Change statistics of objects by doing an ANALYZE;
2. Change some initialization parameters (for example: hash_join_enabled, sort_area_size, db_file_multiblock_read_count).
How can one optimize %XYZ% queries? (for DBA)
It is possible to improve %XYZ% queries by forcing the optimizer to scan all the entries from the index instead of the table. This can be done by specifying hints. If the index is physically smaller than the table (which is usually the case) it will take less time to scan the entire index than to scan the entire table.
What Enter package procedure does ?
Enter Validate-data in the current validation unit.
Where can one find I/O statistics per table? (for DBA)
The UTLESTAT report shows I/O per tablespace but one cannot see what tables in the tablespace has the most I/O. The $ORACLE_HOME/rdbms/admin/catio.sql script creates a sample_io procedure and table to gather the required information. After executing the procedure, one can do a simple SELECT * FROM io_per_object; to extract the required information. For more details, look at the header comments in the $ORACLE_HOME/rdbms/admin/catio.sql script.
My query was fine last week and now it is slow. Why? (for DBA)
The likely cause of this is because the execution plan has changed. Generate a current explain plan of the offending query and compare it to a previous one that was taken when the query was performing well. Usually the previous plan is not available.
Some factors that can cause a plan to change are:
. Which tables are currently analyzed? Were they previously analyzed? (ie. Was the query using RBO and now CBO?)
. Has OPTIMIZER_MODE been changed in INIT.ORA?
. Has the DEGREE of parallelism been defined/changed on any table?
. Have the tables been re-analyzed? Were the tables analyzed using estimate or compute? If estimate, what percentage was used?
. Have the statistics changed?
. Has the INIT.ORA parameter DB_FILE_MULTIBLOCK_READ_COUNT been changed?
. Has the INIT.ORA parameter SORT_AREA_SIZE been changed?
. Have any other INIT.ORA parameters been changed?
. What do you think the plan should be? Run the query with hints to see if this produces the required performance.
Why is Oracle not using the damn index? (for DBA)
This problem normally only arises when the query plan is being generated by the Cost Based Optimizer. The usual cause is because the CBO calculates that executing a Full Table Scan would be faster than accessing the table via the index.
Fundamental things that can be checked are:
. USER_TAB_COLUMNS.NUM_DISTINCT - This column defines the number of distinct values the column holds.
. USER_TABLES.NUM_ROWS - If NUM_DISTINCT = NUM_ROWS then using an index would be preferable to doing a FULL TABLE SCAN. As the NUM_DISTINCT decreases, the cost of using an index increase thereby is making the index less desirable.
. USER_INDEXES.CLUSTERING_FACTOR - This defines how ordered the rows are in the index. If CLUSTERING_FACTOR approaches the number of blocks in the table, the rows are ordered. If it approaches the number of rows in the table, the rows are randomly ordered. In such a case, it is unlikely that index entries in the same leaf block will point to rows in the same data blocks.
. Decrease the INIT.ORA parameter DB_FILE_MULTIBLOCK_READ_COUNT - A higher value will make the cost of a FULL TABLE SCAN cheaper.
. Remember that you MUST supply the leading column of an index, for the index to be used (unless you use a FAST FULL SCAN or SKIP SCANNING).
. There are many other factors that affect the cost, but sometimes the above can help to show why an index is not being used by the CBO. If from checking the above you still feel that the query should be using an index, try specifying an index hint. Obtain an explain plan of the query either using TKPROF with TIMED_STATISTICS, so that one can see the CPU utilization, or with AUTOTRACE to see the statistics. Compare this to the explain plan when not using an index.
When should one rebuild an index? (for DBA)
You can run the 'ANALYZE INDEX VALIDATE STRUCTURE' command on the affected indexes - each invocation of this command creates a single row in the INDEX_STATS view. This row is overwritten by the next ANALYZE INDEX command, so copy the contents of the view into a local table after each ANALYZE. The 'badness' of the index can then be judged by the ratio of 'DEL_LF_ROWS' to 'LF_ROWS'.
What are the unrestricted procedures used to change the popup screen position during run time ?
Anchor-view
Resize -View
Move-View.
What is an Alert ?
An alert is window that appears in the middle of the screen overlaying a portion of the current display.
Deleting a page removes information about all the fields in that page ?
a. True. b. False
a. True.
Two popup pages can appear on the screen at a time ?Two popup pages can appear on the screen at a time ?
a. True. b. False?
a. True.
Classify the restricted and unrestricted procedure from the following.
a. Call
b. User-Exit
c. Call-Query
d. Up
e. Execute-Query
f. Message
g. Exit-From
h. Post
i. Break?

a. Call - unrestricted
b. User Exit - Unrestricted
c. Call_query - Unrestricted
d. Up - Restricted
e. Execute Query - Restricted
f. Message - Restricted
g. Exit_form - Restricted
h. Post - Restricted
i. Break - Unrestricted.
What is an User Exits ?
A user exit is a subroutine which are written in programming languages using pro*C pro *Cobol , etc., that link into the SQL * forms executable.
What is a Trigger ?
A piece of logic that is executed at or triggered by a SQL *forms event.
What is a Package Procedure ?
A Package procedure is built in PL/SQL procedure.
What is the maximum size of a form ?
255 character width and 255 characters Length.
What is the difference between system.current_field and system.cursor_field ?
1. System.current_field gives name of the field.
2. System.cursor_field gives name of the field with block name.
List the system variables related in Block and Field?
1. System.block_status
2. System.current_block
3. System.current_field
4. System.current_value
5. System.cursor_block
6. System.cursor_field
7. System.field_status.
What are the different types of Package Procedure ?
1. Restricted package procedure.
2. Unrestricted package procedure.
What are the types of TRIGGERS ?
1. Navigational Triggers.
2. Transaction Triggers.
Identify package function from the following ?
1. Error-Code
2. Break
3. Call
4. Error-text
5. Form-failure
6. Form-fatal
7. Execute-query
8. Anchor View
9. Message_code?

1. Error_Code
2. Error_Text
3. Form_Failure
4. Form_Fatal
5. Message_Code
Can you attach an lov to a field at run-time? if yes, give the build-in name.?
Yes. Set_item_proprety
Is it possible to attach same library to more than one form?
Yes

Can you attach an lov to a field at design time?
Yes
List the windows event triggers available in Forms 4.0?
When-window-activated,
when-window-closed,
when-window-deactivated,
when-window-resized
What are the triggers associated with the image item?
When-Image-activated(Fires when the operator double clicks on an image Items)
When-image-pressed(fires when the operator selects or deselects the image item)
What is a visual attribute?
Visual Attributes are the font, color and pattern characteristics of objects that operators see and intract with in our application.
How many maximum number of radio buttons can you assign to a radio group?
Unlimited no of radio buttons can be assigned to a radio group

How do you pass the parameters from one form to another form?
To pass one or more parameters to a called form, the calling form must perform the following steps in a trigger or user named routine execute the create_parameter_list built-in function to programmatically. Create a parameter list to execute the add parameter built-in procedure to add one or more parameters list. Execute the call_form, New_form or run_product built_in procedure and include the name or id of the parameter list to be passed to the called form.
What is a Layout Editor?
The Layout Editor is a graphical design facility for creating and arranging items and boilerplate text and graphics objects in your application's interface.
List the Types of Items?
Text item.
Chart item.
Check box.
Display item.
Image item.
List item.
Radio Group.
User Area item.
List system variables available in forms 4.0, and not available in forms 3.0?
System.cordination_operation
System Date_threshold
System.effective_Date
System.event_window
System.suppress_working
What are the display styles of an alert?
Stop, Caution, note

What built-in is used for showing the alert during run-time?
Show_alert.

What built-in is used for changing the properties of the window dynamically?
Set_window_property
Canvas-View
What are the different types of windows?
Root window, secondary window.
What is a predefined exception available in forms 4.0?
Raise form_trigger_failure
What is a radio Group?
Radio groups display a fixed no of options that are mutually Exclusive. User can select one out of n number of options.
What are the different type of a record group?
Query record group
Static record group
Non query record group
What are the menu items that oracle forms 4.0 supports?
Plain, Check,Radio, Separator, Magic
Give the equivalent term in forms 4.0 for the following. Page, Page 0?
Page - Canvas-View
Page 0 - Canvas-view null.
What triggers are associated with the radio group?
Only when-radio-changed trigger associated with radio group
Visual Attributes.

What are the triggers associated with a check box?
Only When-checkbox-activated Trigger associated with a Check box.
Can you attach an alert to a field?
No
Can a root window be made modal?
No
What is a list item?
It is a list of text elements.
List some built-in routines used to manipulate images in image_item?
Image_add
Image_and
Image_subtract
Image_xor
Image_zoom
Can you change the alert messages at run-time?
If yes, give the name of the built-in to change the alert messages at run-time. Yes. Set_alert_property.
What is the built-in used to get and set lov properties during run-time?
Get_lov_property
Set_lov_property
Record Group
What is the built-in routine used to count the no of rows in a group?
Get_group _row_count
System Variables
Give the Types of modules in a form?
Form
Menu
Library
Write the Abbreviation for the following File Extension 1. FMB 2. MMB 3. PLL?
FMB ----- Form Module Binary.
MMB ----- Menu Module Binary.
PLL ------ PL/SQL Library Module Binary.
List the built-in routine for controlling window during run-time?
Find_window,
get_window_property,
hide_window,
move_window,
resize_window,
set_window_property,
show_View
List the built-in routine for controlling window during run-time?
Find_canvas
Get-Canvas_property
Get_view_property
Hide_View
Replace_content_view
Scroll_view
Set_canvas_property
Set_view_property
Show_view
Alert
What is the built-in function used for finding the alert?
Find_alert
Editors

List the editors availables in forms 4.0?
Default editor
User_defined editors
system editors.

What buil-in routines are used to display editor dynamically?
Edit_text item
show_editor
LOV
What is an Lov?
A list of values is a single or multi column selection list displayed in a pop-up window
What is a record Group?
A record group is an internal oracle forms data structure that has a similar column/row frame work to a database table
Give built-in routine related to a record groups?
Create_group (Function)
Create_group_from_query(Function)
Delete_group(Procedure)
Add_group_column(Function)
Add_group_row(Procedure)
Delete_group_row(Procedure)
Populate_group(Function)
Populate_group_with_query(Function)
Set_group_Char_cell(procedure)
List the built-in routines for the controlling canvas views during run-time?
Find_canvas
Get-Canvas_property
Get_view_property
Hide_View
Replace_content_view
Scroll_view
Set_canvas_property
Set_view_property
Show_view
Alert
System.effective_date system variable is read only True/False?
False
What are the built_in used to trapping errors in forms 4?
Error_type return character
Error_code return number
Error_text return char
Dbms_error_code return no.
Dbms_error_text return char
What is Oracle Financials? (for DBA)
Oracle Financials products provide organizations with solutions to a wide range of long- and short-term accounting system issues. Regardless of the size of the business, Oracle Financials can meet accounting management demands with:
Oracle Assets: Ensures that an organization's property and equipment investment is accurate and that the correct asset tax accounting strategies are chosen.
Oracle General Ledger: Offers a complete solution to journal entry, budgeting, allocations, consolidation, and financial reporting needs.
Oracle Inventory: Helps an organization make better inventory decisions by minimizing stock and maximizing cash flow.
Oracle Order Entry: Provides organizations with a sophisticated order entry system for managing customer commitments.
Oracle Payables: Lets an organization process more invoices with fewer staff members and tighter controls. Helps save money through maximum discounts, bank float, and prevention of duplicate payment.
Oracle Personnel: Improves the management of employee- related issues by retaining and making available every form of personnel data.
Oracle Purchasing: Improves buying power, helps negotiate bigger discounts, eliminates paper flow, increases financial controls, and increases productivity.
Oracle Receivables:. Improves cash flow by letting an organization process more payments faster, without off-line research. Helps correctly account for cash, reduce outstanding receivables, and improve collection effectiveness.
Oracle Revenue Accounting Gives an organization timely and accurate revenue and flexible commissions reporting.
Oracle Sales Analysis: Allows for better forecasting, planning. and reporting of sales information.
What are the design facilities available in forms 4.0?
Default Block facility.
Layout Editor.
Menu Editor.
Object Lists.
Property Sheets.
PL/SQL Editor.
Tables Columns Browser.
Built-ins Browser.
What is the most important module in Oracle Financials? (for DBA)
The General Ledger (GL) module is the basis for all other Oracle Financial modules. All other modules provide information to it. If you implement Oracle Financials, you should switch your current GL system first.GL is relatively easy to implement. You should go live with it first to give your implementation team a chance to be familiar with Oracle Financials.
What are the types of canvas-views?
Content View, Stacked View.
What is the MultiOrg and what is it used for? (for DBA)
MultiOrg or Multiple Organizations Architecture allows multiple operating units and their relationships to be defined within a single installation of Oracle Applications. This keeps each operating unit's transaction data separate and secure.
Use the following query to determine if MuliOrg is intalled:
select multi_org_flag from fnd_product_groups;
What is the difference between Fields and FlexFields? (for DBA)
A field is a position on a form that one uses to enter, view, update, or delete information. A field prompt describes each field by telling what kind of information appears in the field, or alternatively, what kind of information should be entered in the field.
A flexfield is an Oracle Applications field made up of segments. Each segment has an assigned name and a set of valid values. Oracle Applications uses flexfields to capture information about your organization. There are two types of flexfields: key flexfields and descriptive flexfields.
Explain types of Block in forms4.0?
Base table Blocks.
Control Blocks.
1. A base table block is one that is associated with a specific database table or view.
2. A control block is a block that is not associated with a database table. ITEMS
What is an Alert?
An alert is a modal window that displays a message notifies the operator of some application condition
What are the built-in routines is available in forms 4.0 to create and manipulate a parameter list?
Add_parameter
Create_Parameter_list
Delete_parameter
Destroy_parameter_list
Get_parameter_attr
Get_parameter_list
set_parameter_attr
What is a record Group?
A record group is an internal oracle forms data structure that has a similar column/row frame work to a database table
What is a Navigable item?
A navigable item is one that operators can navigate to with the keyboard during default navigation, or that Oracle forms can navigate to by executing a navigational built-in procedure.
What is a library in Forms 4.0?
A library is a collection of Pl/SQL program units, including user named procedures, functions & packages
How image_items can be populate to field in forms 4.0?
A fetch from a long raw database column PL/Sql assignment to executing the read_image_file built_in procedure to get an image from the file system.
What is the content view and stacked view?
A content view is the "Base" view that occupies the entire content pane of the window in which it is displayed. A stacked view differs from a content canvas view in that it is not the base view for the window to which it is assigned

What is a Check Box?
A Check Box is a two state control that indicates whether a certain condition or value is on or off, true or false. The display state of a check box is always either "checked" or "unchecked".
What is a canvas-view?
A canvas-view is the background object on which you layout the interface items (text-items, check boxes, radio groups, and so on.) and boilerplate objects that operators see and interact with as they run your form. At run-time, operators can see only those items that have been assigned to a specific canvas. Each canvas, in term, must be displayed in a specific window.
Explain the following file extension related to library?
.pll,.lib,.pld
The library pll files is a portable design file comparable to an fmb form file
The library lib file is a plat form specific, generated library file comparable to a fmx form file
The pld file is Txt format file and can be used for source controlling your library files Parameter
Explain the usage of WHERE CURRENT OF clause in cursors ?
WHERE CURRENT OF clause in an UPDATE,DELETE statement refers to the latest row fetched from a cursor. Database Triggers
Name the tables where characteristics of Package, procedure and functions are stored ?
User_objects, User_Source and User_error.
Explain the two type of Cursors ?
There are two types of cursors, Implicit Cursor and Explicit Cursor. PL/SQL uses Implicit Cursors for queries. User defined cursors are called Explicit Cursors. They can be declared and used.
What are two parts of package ?
The two parts of package are PACKAGE SPECIFICATION & PACKAGE BODY. Package Specification contains declarations that are global to the packages and local to the schema. Package Body contains actual procedures and local declaration of the procedures and cursor declarations.
What are two virtual tables available during database trigger execution ?
The table columns are referred as OLD.column_name and NEW.column_name.
For triggers related to INSERT only NEW.column_name values only available.
For triggers related to UPDATE only OLD.column_name NEW.column_name values only available.
For triggers related to DELETE only OLD.column_name values only available.
What is Fine Grained Auditing? (for DBA)
Fine Grained Auditing (DBMS_FGA) allows auditing records to be generated when certain rows are selected from a table. A list of defined policies can be obtained from DBA_AUDIT_POLICIES. Audit records are stored in DBA_FGA_AUDIT_TRAIL. Look at this example:
o Add policy on table with autiting condition...
execute dbms_fga.add_policy('HR', 'EMP', 'policy1', 'deptno > 10');
o Must ANALYZE, this feature works with CBO (Cost Based Optimizer)
analyze table EMP compute statistics;
select * from EMP where c1 = 11; -- Will trigger auditing
select * from EMP where c1 = 09; -- No auditing
o Now we can see the statments that triggered the auditing condition...
select sqltext from sys.fga_log$;
delete from sys.fga_log$;

What is a package ? What are the advantages of packages ? What is Pragma EXECPTION_INIT ? Explain the usage ?
The PRAGMA EXECPTION_INIT tells the complier to associate an exception with an oracle error. To get an error message of a specific oracle error. e.g. PRAGMA EXCEPTION_INIT (exception name, oracle error number)
What is a Virtual Private Database? (for DBA)
Oracle 8i introduced the notion of a Virtual Private Database (VPD). A VPD offers Fine-Grained Access Control (FGAC) for secure separation of data. This ensures that users only have access to data that pertains to them. Using this option, one could even store multiple companies' data within the same schema, without them knowing about it. VPD configuration is done via the DBMS_RLS (Row Level Security) package. Select from SYS.V$VPD_POLICY to see existing VPD configuration.
What is Raise_application_error ?
Raise_application_error is a procedure of package DBMS_STANDARD which allows to issue an user_defined error messages from stored sub-program or database trigger.
What is Oracle Label Security? (for DBA)
Oracle Label Security (formerly called Trusted Oracle MLS RDBMS) uses the VPD (Virtual Private Database) feature of Oracle8i to implement row level security. Access to rows are restricted according to a user's security sensitivity tag or label. Oracle Label Security is configured, controlled and managed from the Policy Manager, an Enterprise Manager-based GUI utility.
Give the structure of the procedure ?
PROCEDURE name (parameter list.....)
is
local variable declarations
BEGIN
Executable statements.
Exception.
exception handlers
end;
What is OEM (Oracle Enterprise Manager)? (for DBA)
OEM is a set of systems management tools provided by Oracle Corporation for managing the Oracle environment. It provides tools to monitor the Oracle environment and automate tasks (both one-time and repetitive in nature) to take database administration a step closer to "Lights Out" management.
Question What is PL/SQL ?
PL/SQL is a procedural language that has both interactive SQL and procedural programming language constructs such as iteration, conditional branching.
What are the components of OEM? (for DBA)
Oracle Enterprise Manager (OEM) has the following components:
. Management Server (OMS): Middle tier server that handles communication with the intelligent agents. The OEM Console connects to the management server to monitor and configure the Oracle enterprise.
. Console: This is a graphical interface from where one can schedule jobs, events, and monitor the database. The console can be opened from a Windows workstation, Unix XTerm (oemapp command) or Web browser session (oem_webstage).
. Intelligent Agent (OIA): The OIA runs on the target database and takes care of the execution of jobs and events scheduled through the Console.
What happens if a procedure that updates a column of table X is called in a database trigger of the same table ?
Mutation of table occurs.
Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger ? Why ?
It is not possible. As triggers are defined for each table, if you use COMMIT of ROLLBACK in a trigger, it affects logical transaction processing.
How many types of database triggers can be specified on a table ? What are they ?
Insert Update Delete
Before Row o.k. o.k. o.k.
After Row o.k. o.k. o.k.
Before Statement o.k. o.k. o.k.
After Statement o.k. o.k. o.k.
If FOR EACH ROW clause is specified, then the trigger for each Row affected by the statement.
If WHEN clause is specified, the trigger fires according to the returned Boolean value.
What are the modes of parameters that can be passed to a procedure ?
IN,OUT,IN-OUT parameters.

Where the Pre_defined_exceptions are stored ?
In the standard package.
Procedures, Functions & Packages ;
Write the order of precedence for validation of a column in a table ?
I. done using Database triggers.
ii. done using Integarity Constraints.?

I & ii.
Give the structure of the function ?
FUNCTION name (argument list .....) Return datatype is
local variable declarations
Begin
executable statements
Exception
execution handlers
End;
Explain how procedures and functions are called in a PL/SQL block ?
Function is called as part of an expression.
sal := calculate_sal ('a822');
procedure is called as a PL/SQL statement
calculate_bonus ('A822');

What are advantages fo Stored Procedures?
Extensibility,Modularity, Reusability, Maintainability and one time compilation.
What is an Exception ? What are types of Exception ?
Exception is the error handling part of PL/SQL block. The types are Predefined and user defined. Some of Predefined exceptions are.
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
NO_DATA_FOUND
TOO_MANY_ROWS
INVALID_CURSOR
INVALID_NUMBER
LOGON_DENIED
NOT_LOGGED_ON
PROGRAM-ERROR
STORAGE_ERROR
TIMEOUT_ON_RESOURCE
VALUE_ERROR
ZERO_DIVIDE
OTHERS.
What are the PL/SQL Statements used in cursor processing ?
DECLARE CURSOR name, OPEN cursor name, FETCH cursor name INTO or Record types, CLOSE cursor name.
What are the components of a PL/SQL Block ?
Declarative part, Executable part and Exception part.
Datatypes PL/SQL
What is a database trigger ? Name some usages of database trigger ?
Database trigger is stored PL/SQL program unit associated with a specific database table. Usages are Audit data modifications, Log events transparently, Enforce complex business rules Derive column values automatically, Implement complex security authorizations. Maintain replicate tables.
What is a cursor ? Why Cursor is required ?
Cursor is a named private SQL area from where information can be accessed. Cursors are required to process rows individually for queries returning multiple rows.
What is a cursor for loop ?
Cursor for loop implicitly declares %ROWTYPE as loop index, opens a cursor, fetches rows of values from active set into fields in the record and closes when all the records have been processed.
e.g.. FOR emp_rec IN C1 LOOP
salary_total := salary_total +emp_rec sal;
END LOOP;

What will happen after commit statement ?
Cursor C1 is
Select empno,
ename from emp;
Begin
open C1; loop
Fetch C1 into
eno.ename;
Exit When
C1 %notfound;-----
commit;
end loop;
end;
The cursor having query as SELECT .... FOR UPDATE gets closed after COMMIT/ROLLBACK.
The cursor having query as SELECT.... does not get closed even after COMMIT/ROLLBACK.
How packaged procedures and functions are called from the following?
a. Stored procedure or anonymous block
b. an application program such a PRC *C, PRO* COBOL
c. SQL *PLUS??

a. PACKAGE NAME.PROCEDURE NAME (parameters);
variable := PACKAGE NAME.FUNCTION NAME (arguments);
EXEC SQL EXECUTE
b.BEGIN
PACKAGE NAME.PROCEDURE NAME (parameters)
variable := PACKAGE NAME.FUNCTION NAME (arguments);
END;
END EXEC;
c. EXECUTE PACKAGE NAME.PROCEDURE if the procedures does not have any out/in-out parameters. A function can not be called.
What is a stored procedure ?
A stored procedure is a sequence of statements that perform specific function.
What are the components of a PL/SQL block ?
A set of related declarations and procedural statements is called block.
What is difference between a PROCEDURE & FUNCTION ?
A FUNCTION is always returns a value using the return statement.
A PROCEDURE may return one or more values through parameters or may not return at all.
What is difference between a Cursor declared in a procedure and Cursor declared in a package specification ?
A cursor declared in a package specification is global and can be accessed by other procedures or procedures in a package.
A cursor declared in a procedure is local to the procedure that can not be accessed by other procedures.
What are the cursor attributes used in PL/SQL ?
%ISOPEN - to check whether cursor is open or not
% ROWCOUNT - number of rows fetched/updated/deleted.
% FOUND - to check whether cursor has fetched any row. True if rows are fetched.
% NOT FOUND - to check whether cursor has fetched any row. True if no rows are featched.
These attributes are proceeded with SQL for Implicit Cursors and with Cursor name for Explicit Cursors.
What are % TYPE and % ROWTYPE ? What are the advantages of using these over datatypes?
% TYPE provides the data type of a variable or a database column to that variable.
% ROWTYPE provides the record type that represents a entire row of a table or view or columns selected in the cursor.
The advantages are :
I. Need not know about variable's data type
ii. If the database definition of a column in a table changes, the data type of a variable changes accordingly.
What is difference between % ROWTYPE and TYPE RECORD ?
% ROWTYPE is to be used whenever query returns a entire row of a table or view.
TYPE rec RECORD is to be used whenever query returns columns of different table or views and variables.
E.g. TYPE r_emp is RECORD (eno emp.empno% type,ename emp ename %type );
e_rec emp% ROWTYPE
cursor c1 is select empno,deptno from emp;
e_rec c1 %ROWTYPE.
What are the different types of PL/SQL program units that can be defined and stored in ORACLE database ?
Procedures and Functions,Packages and Database Triggers.
What are the advantages of having a Package ?
Increased functionality (for example,global package variables can be declared and used by any proecdure in the package) and performance (for example all objects of the package are parsed compiled, and loaded into memory once)
What are the uses of Database Trigger ?
Database triggers can be used to automatic data generation, audit data modifications, enforce complex Integrity constraints, and customize complex security authorizations.
What is a Procedure ?
A Procedure consist of a set of SQL and PL/SQL statements that are grouped together as a unit to solve a specific problem or perform a set of related tasks.
What is a Package ?
A Package is a collection of related procedures, functions, variables and other package constructs together as a unit in the database.
What is difference between Procedures and Functions ?
A Function returns a value to the caller where as a Procedure does not.
What is Database Trigger ?
A Database Trigger is procedure (set of SQL and PL/SQL statements) that is automatically executed as a result of an insert in, update to, or delete from a table.
Can the default values be assigned to actual parameters?
Yes

Can a primary key contain more than one columns?
Yes
What is an UTL_FILE.What are different procedures and functions associated with it?
UTL_FILE is a package that adds the ability to read and write to operating system files. Procedures associated with it are FCLOSE, FCLOSE_ALL and 5 procedures to output data to a file PUT, PUT_LINE, NEW_LINE, PUTF, FFLUSH.PUT, FFLUSH.PUT_LINE,FFLUSH.NEW_LINE. Functions associated with it are FOPEN, ISOPEN.
What are ORACLE PRECOMPILERS?
Using ORACLE PRECOMPILERS, SQL statements and PL/SQL blocks can be contained inside 3GL programs written in C,C++,COBOL,PASCAL, FORTRAN,PL/1 AND ADA. The Precompilers are known as Pro*C,Pro*Cobol,... This form of PL/SQL is known as embedded pl/sql,the language in which pl/sql is embedded is known as the host language. The prcompiler translates the embedded SQL and pl/sql statements into calls to the precompiler runtime library. The output must be compiled and linked with this library to creator an executable.
Differentiate between TRUNCATE and DELETE?
TRUNCATE deletes much faster than DELETE
TRUNCATE
DELETE
It is a DDL statement
It is a DML statement
It is a one way trip, cannot ROLLBACK
One can Rollback
Doesn't have selective features (where clause)
Has
Doesn't fire database triggers
Does
It requires disabling of referential constraints.
What is difference between a formal and an actual parameter?
The variables declared in the procedure and which are passed, as arguments are called actual, the parameters in the procedure declaration. Actual parameters contain the values that are passed to a procedure and receive results. Formal parameters are the placeholders for the values of actual parameters

What should be the return type for a cursor variable. Can we use a scalar data type as return type?
The return type for a cursor must be a record type.It can be declared explicitly as a user-defined or %ROWTYPE can be used. eg TYPE t_studentsref IS REF CURSOR RETURN students%ROWTYPE
What are different Oracle database objects?
-TABLES
-VIEWS
-INDEXES
-SYNONYMS
-SEQUENCES
-TABLESPACES etc

What is difference between SUBSTR and INSTR?
SUBSTR returns a specified portion of a string eg SUBSTR('BCDEF',4) output BCDE INSTR provides character position in which a pattern is found in a string. eg INSTR('ABC-DC-F','-',2) output 7 (2nd occurence of '-')
Display the number value in Words?
SQL> select sal, (to_char(to_date(sal,'j'), 'jsp'))
from emp;
the output like,
SAL (TO_CHAR(TO_DATE(SAL,'J'),'JSP'))
--------- ----------------------------------------
800 eight hundred
1600 one thousand six hundred
1250 one thousand two hundred fifty
If you want to add some text like, Rs. Three Thousand only.
SQL> select sal "Salary ",
(' Rs. '|| (to_char(to_date(sal,'j'), 'Jsp'))|| ' only.'))
"Sal in Words" from emp
/
Salary Sal in Words
------- -----------------------------------------------
800 Rs. Eight Hundred only.
1600 Rs. One Thousand Six Hundred only.
1250 Rs. One Thousand Two Hundred Fifty only.
What is difference between SQL and SQL*PLUS?
SQL*PLUS is a command line tool where as SQL and PL/SQL language interface and reporting tool. Its a command line tool that allows user to type SQL commands to be executed directly against an Oracle database. SQL is a language used to query the relational database(DML,DCL,DDL). SQL*PLUS commands are used to format query result, Set options, Edit SQL commands and PL/SQL.
What are various joins used while writing SUBQUERIES?
Self join-Its a join foreign key of a table references the same table. Outer Join--Its a join condition used where One can query all the rows of one of the tables in the join condition even though they don't satisfy the join condition.
Equi-join--Its a join condition that retrieves rows from one or more tables in which one or more columns in one table are equal to one or more columns in the second table.
What a SELECT FOR UPDATE cursor represent.?
SELECT......FROM......FOR......UPDATE[OF column-reference][NOWAIT]
The processing done in a fetch loop modifies the rows that have been retrieved by the cursor. A convenient way of modifying the rows is done by a method with two parts: the FOR UPDATE clause in the cursor declaration, WHERE CURRENT OF CLAUSE in an UPDATE or declaration statement.
What are various privileges that a user can grant to another user?
-SELECT
-CONNECT
-RESOURCES
Display the records between two range?
select rownum, empno, ename from emp where rowid in (select rowid from emp where rownum <=&upto minus select rowid from emp where rownum<&Start);
minvalue.sql Select the Nth lowest value from a table?
select level, min('col_name') from my_table where level = '&n' connect by prior ('col_name') < 'col_name')
group by level;
Example:
Given a table called emp with the following columns:
-- id number
-- name varchar2(20)
-- sal number
--
-- For the second lowest salary:
-- select level, min(sal) from emp
-- where level=2
-- connect by prior sal < sal
-- group by level
What is difference between Rename and Alias?
Rename is a permanent name given to a table or column whereas Alias is a temporary name given to a table or column which do not exist once the SQL statement is executed.
Difference between an implicit & an explicit cursor.?
only one row. However,queries that return more than one row you must declare an explicit cursor or use a cursor FOR loop. Explicit cursor is a cursor in which the cursor name is explicitly assigned to a SELECT statement via the CURSOR...IS statement. An implicit cursor is used for all SQL statements Declare, Open, Fetch, Close. An explicit cursors are used to process multirow SELECT statements An implicit cursor is used to process INSERT, UPDATE, DELETE and single row SELECT. .INTO statements.
What is a OUTER JOIN?
Outer Join--Its a join condition used where you can query all the rows of one of the tables in the join condition even though they don't satisfy the join condition.
What is a cursor?
Oracle uses work area to execute SQL statements and store processing information PL/SQL construct called a cursor lets you name a work area and access its stored information A cursor is a mechanism used to fetch more than one row in a Pl/SQl block.
What is the purpose of a cluster?
Oracle does not allow a user to specifically locate tables, since that is a part of the function of the RDBMS. However, for the purpose of increasing performance, oracle allows a developer to create a CLUSTER. A CLUSTER provides a means for storing data from different tables together for faster retrieval than if the table placement were left to the RDBMS.

What is OCI. What are its uses?
Oracle Call Interface is a method of accesing database from a 3GL program. Uses--No precompiler is required,PL/SQL blocks are executed like other DML statements.
The OCI library provides
--functions to parse SQL statemets
--bind input variables
--bind output variables
--execute statements
--fetch the results
How you open and close a cursor variable. Why it is required?
OPEN cursor variable FOR SELECT...Statement
CLOSE cursor variable In order to associate a cursor variable with a particular SELECT statement OPEN syntax is used. In order to free the resources used for the query CLOSE statement is used.

Display Odd/ Even number of records?
Odd number of records:
select * from emp where (rowid,1) in (select rowid, mod(rownum,2) from emp);
Output:-
1
3
5
Even number of records:
select * from emp where (rowid,0) in (select rowid, mod(rownum,2) from emp)
Output:-
2
4
6
What are various constraints used in SQL?
-NULL
-NOT NULL
-CHECK
-DEFAULT
Can cursor variables be stored in PL/SQL tables. If yes how. If not why?
No, a cursor variable points a row which cannot be stored in a two-dimensional PL/SQL table.
Difference between NO DATA FOUND and %NOTFOUND?
NO DATA FOUND is an exception raised only for the SELECT....INTO statements when the where clause of the querydoes not match any rows. When the where clause of the explicit cursor does not match any rows the %NOTFOUND attribute is set to TRUE instead.
Can you use a commit statement within a database trigger?
No
What WHERE CURRENT OF clause does in a cursor?
LOOP
SELECT num_credits INTO v_numcredits FROM classes
WHERE dept=123 and course=101;
UPDATE students
FHKO;;;;;;;;;SET current_credits=current_credits+v_numcredits
WHERE CURRENT OF X;
There is a string 120000 12 0 .125 , how you will find the position of the decimal place?
INSTR('120000 12 0 .125',1,'.')
output 13
What are different modes of parameters used in functions and procedures?
-IN -OUT -INOUT
How you were passing cursor variables in PL/SQL 2.2?
In PL/SQL 2.2 cursor variables cannot be declared in a package.This is because the storage for a cursor variable has to be allocated using Pro*C or OCI with version 2.2, the only means of passing a cursor variable to a PL/SQL block is via bind variable or a procedure parameter.
When do you use WHERE clause and when do you use HAVING clause?
HAVING clause is used when you want to specify a condition for a group function and it is written after GROUP BY clause. The WHERE clause is used when you want to specify a condition for columns, single row functions except group functions and it is written before GROUP BY clause if it is used.
Difference between procedure and function.?
Functions are named PL/SQL blocks that return a value and can be called with arguments procedure a named block that can be called with parameter. A procedure all is a PL/SQL statement by itself, while a Function call is called as part of an expression.
Which is more faster - IN or EXISTS?
EXISTS is more faster than IN because EXISTS returns a Boolean value whereas IN returns a value.
What is syntax for dropping a procedure and a function .Are these operations possible?
Drop Procedure procedure_name
Drop Function function_name
How will you delete duplicating rows from a base table?
delete from table_name where rowid not in (select max(rowid) from table group by duplicate_values_field_name); or delete duplicate_values_field_name dv from table_name ta where rowid <(select min(rowid) from table_name tb where ta.dv=tb.dv);
Difference between database triggers and form triggers?
-Data base trigger(DBT) fires when a DML operation is performed on a data base table. Form trigger(FT) Fires when user presses a key or navigates between fields on the screen
-Can be row level or statement level No distinction between row level and statement level.
-Can manipulate data stored in Oracle tables via SQL Can manipulate data in Oracle tables as well as variables in forms.
-Can be fired from any session executing the triggering DML statements. Can be fired only from the form that define the trigger.
-Can cause other database triggers to fire. Can cause other database triggers to fire, but not other form triggers.
What is a cursor for loop?
Cursor For Loop is a loop where oracle implicitly declares a loop variable, the loop index that of the same record type as the cursor's record.
How you will avoid duplicating records in a query?
By using DISTINCT
What is a view ?
A view is stored procedure based on one or more tables, it's a virtual table.
What is difference between UNIQUE and PRIMARY KEY constraints?
A table can have only one PRIMARY KEY whereas there can be any number of UNIQUE keys. The columns that compose PK are automatically define NOT NULL, whereas a column that compose a UNIQUE is not automatically defined to be mandatory must also specify the column is NOT NULL.
What is use of a cursor variable? How it is defined?
A cursor variable is associated with different statements at run time, which can hold different values at run time. Static cursors can only be associated with one run time query. A cursor variable is reference type (like a pointer in C).
Declaring a cursor variable:
TYPE type_name IS REF CURSOR RETURN return_type type_name is the name of the reference type,return_type is a record type indicating the types of the select list that will eventually be returned by the cursor variable.
How do you find the numbert of rows in a Table ?
A bad answer is count them (SELECT COUNT(*) FROM table_name)
A good answer is :-
'By generating SQL to ANALYZE TABLE table_name COUNT STATISTICS by querying Oracle System Catalogues (e.g. USER_TABLES or ALL_TABLES).
The best answer is to refer to the utility which Oracle released which makes it unnecessary to do ANALYZE TABLE for each Table individually.

What is the maximum buffer size that can be specified using the DBMS_OUTPUT.ENABLE function?
1,000,00
What are cursor attributes?
-%ROWCOUNT
-%NOTFOUND
-%FOUND
-%ISOPEN
There is a % sign in one field of a column. What will be the query to find it?
'' Should be used before '%'.
What is ON DELETE CASCADE ?
When ON DELETE CASCADE is specified ORACLE maintains referential integrity by automatically removing dependent foreign key values if a referenced primary or unique key value is removed.
What is the fastest way of accessing a row in a table ?
Using ROWID.CONSTRAINTS
What is difference between TRUNCATE & DELETE ?
TRUNCATE commits after deleting entire table i.e., can not be rolled back. Database triggers do not fire on TRUNCATEDELETE allows the filtered deletion. Deleted records can be rolled back or committed. Database triggers fire on DELETE.
What is a transaction ?
Transaction is logical unit between two commits and commit and rollback.
What are the advantages of VIEW ?
To protect some of the columns of a table from other users.To hide complexity of a query.To hide complexity of calculations.
How will you a activate/deactivate integrity constraints ?
The integrity constraints can be enabled or disabled by ALTER TABLE ENABLE constraint/DISABLE constraint.
Where the integrity constraints are stored in Data Dictionary ?
The integrity constraints are stored in USER_CONSTRAINTS.
What is the Subquery ?
Sub query is a query whose return values are used in filtering conditions of the main query.
How to access the current value and next value from a sequence ? Is it possible to access the current value in a session before accessing next value ?
Sequence name CURRVAL, Sequence name NEXTVAL.It is not possible. Only if you access next value in the session, current value can be accessed.
What are the usage of SAVEPOINTS ?value in a session before accessing next value ?
SAVEPOINTS are used to subdivide a transaction into smaller parts. It enables rolling back part of a transaction. Maximum of five save points are allowed.
What is ROWID ?in a session before accessing next value ?
ROWID is a pseudo column attached to each row of a table. It is 18 character long, blockno, rownumber are the components of ROWID.
Explain Connect by Prior ?in a session before accessing next value ?
Retrieves rows in hierarchical order.e.g. select empno, ename from emp where.
How many LONG columns are allowed in a table ? Is it possible to use LONG columns in WHERE clause or ORDER BY ?
Only one LONG columns is allowed. It is not possible to use LONG column in WHERE or ORDER BY clause.
What is Referential Integrity ?
Maintaining data integrity through a set of rules that restrict the values of one or more columns of the tables based on the values of primary key or unique key of the referenced table.
What is a join ? Explain the different types of joins ?
Join is a query which retrieves related columns or rows from multiple tables.Self Join - Joining the table with itself.Equi Join - Joining two tables by equating two common columns.Non-Equi Join - Joining two tables by equating two common columns.Outer Join - Joining two tables in such a way that query can also retrieve rows that do not have corresponding join value in the other table.
If an unique key constraint on DATE column is created, will it validate the rows that are inserted with SYSDATE ?
It won't, Because SYSDATE format contains time attached with it.
How does one stop and start the OMS? (for DBA)
Use the following command sequence to stop and start the OMS (Oracle Management Server):
oemctl start oms
oemctl status oms sysman/oem_temp
oemctl stop oms sysman/oem_temp
Windows NT/2000 users can just stop and start the required services. The default OEM administrator is "sysman" with a password of "oem_temp".
NOTE: Use command oemctrl instead of oemctl for Oracle 8i and below.
What is an Integrity Constraint ?
Integrity constraint is a rule that restricts values to a column in a table.
How does one create a repository? (for DBA)
For OEM v2 and above, start the Oracle Enterprise Manager Configuration Assistant (emca on Unix) to create and configure the management server and repository. Remember to setup a backup for the repository database after creating it.
If a View on a single base table is manipulated will the changes be reflected on the base table ?
If changes are made to the tables which are base tables of a view will the changes be reference on the view.

The following describes means to create a OEM V1.x (very old!!!) repository on WindowsNT:

. Create a tablespace that would hold the repository data. A size between 200- 250 MB would be ideal. Let us call it Dummy_Space.
. Create an Oracle user who would own this repository. Assign DBA, SNMPAgent, Exp_Full_database, Imp_Full_database roles to this user. Lets call this user Dummy_user. Assign Dummy_Space as the default tablespace.
. Create an operating system user with the same name as the Oracle username. I.e. Dummy_User. Add 'Log on as a batch job' under advanced rights in User manager.
. Fire up Enterprise manager and log in as Dummy_User and enter the password. This would trigger the creation of the repository. From now on, Enterprise manager is ready to accept jobs.
What is a database link ?
Database Link is a named path through which a remote database can be accessed.
How does one list one's databases in the OEM Console? (for DBA)
Follow these steps to discover databases and other services from the OEM Console:
1. Ensure the GLOBAL_DBNAME parameter is set for all databases in your LISTENER.ORA file (optional). These names will be listed in the OEM Console. Please note that names entered are case sensitive. A portion of a listener.ora file:
(SID_DESC =
(GLOBAL_DBNAME = DB_name_for_OEM)
(SID_NAME = ...
2. Start the Oracle Intelligent Agent on the machine you want to discover. See section "How does one start the Oracle Intelligent Agent?".
3. Start the OEM Console, navigate to menu "Navigator/ Discover Nodes". The OEM Discovery Wizard will guide you through the process of discovering your databases and other services.

What is CYCLE/NO CYCLE in a Sequence ?
CYCLE specifies that the sequence continues to generate values after reaching either maximum or minimum value. After pan ascending sequence reaches its maximum value, it generates its minimum value. After a descending sequence reaches its minimum, it generates its maximum.NO CYCLE specifies that the sequence cannot generate more values after reaching its maximum or minimum value.
What is correlated sub-query ?
Correlated sub query is a sub query which has reference to the main query.
What are the data types allowed in a table ?
CHAR,VARCHAR2,NUMBER,DATE,RAW,LONG and LONG RAW.
What is difference between CHAR and VARCHAR2 ? What is the maximum SIZE allowed for each type ?
CHAR pads blank spaces to the maximum length. VARCHAR2 does not pad blank spaces. For CHAR it is 255 and 2000 for VARCHAR2.
Can a view be updated/inserted/deleted? If Yes under what conditions ?
A View can be updated/deleted/inserted if it has only one base table if the view is based on columns from one or more tables then insert, update and delete is not possible.
What are the different types of Coordinations of the Master with the Detail block?
POPULATE_GROUP(function)
POPULATE_GROUP_WITH_QUERY(function)
SET_GROUP_CHAR_CELL(procedure)
SET_GROUPCELL(procedure)
SET_GROUP_NUMBER_CELL(procedure)
Use the ADD_GROUP_COLUMN function to add a column to a record group that was created at design time?
I) TRUE II) FALSE
II) FALSE
Use the ADD_GROUP_ROW procedure to add a row to a static record group?
I) TRUE II) FALSE
I) FALSE
maxvalue.sql Select the Nth Highest value from a table?
select level, max('col_name') from my_table where level = '&n' connect by prior ('col_name') > 'col_name')
group by level;
Example:
Given a table called emp with the following columns:
-- id number
-- name varchar2(20)
-- sal number
--
-- For the second highest salary:
-- select level, max(sal) from emp
-- where level=2
-- connect by prior sal > sal
-- group by level
Find out nth highest salary from emp table?
SELECT DISTINCT (a.sal) FROM EMP A WHERE &N = (SELECT COUNT (DISTINCT (b.sal)) FROM EMP B WHERE a.sal<=b.sal);
For E.g.:-
Enter value for n: 2
SAL
---------
3700
Suppose a customer table is having different columns like customer no, payments.What will be the query to select top three max payments?
SELECT customer_no, payments from customer C1
WHERE 3<=(SELECT COUNT(*) from customer C2
WHERE C1.payment <= C2.payment)
How you will avoid your query from using indexes?
SELECT * FROM emp
Where emp_no+' '=12345;
i.e you have to concatenate the column name with space within codes in the where condition.
SELECT /*+ FULL(a) */ ename, emp_no from emp
where emp_no=1234;
i.e using HINTS
What utility is used to create a physical backup?
Either rman or alter tablespace begin backup will do..
What are the Back ground processes in Oracle and what are they.
This is one of the most frequently asked question.There are basically 9 Processes but in a general system we need to mention the first five background processes.They do the house keeping activities for the Oracle and are common in any system.
The various background processes in oracle are
a) Data Base Writer(DBWR) :: Data Base Writer Writes Modified blocks from Database buffer cache to Data Files.This is required since the data is not written whenever a transaction is committed.
b)LogWriter(LGWR) :: LogWriter writes the redo log entries to disk. Redo Log data is generated in redo log buffer of SGA. As transaction commits and log buffer fills, LGWR writes log entries into a online redo log file.
c) System Monitor(SMON) :: The System Monitor performs instance recovery at instance startup. This is useful for recovery from system failure
d)Process Monitor(PMON) :: The Process Monitor performs process recovery when user Process fails. Pmon Clears and Frees resources that process was using.
e) CheckPoint(CKPT) :: At Specified times, all modified database buffers in SGA are written to data files by DBWR at Checkpoints and Updating all data files and control files of database to indicate the most recent checkpoint
f)Archieves(ARCH) :: The Archiver copies online redo log files to archival storal when they are busy.
g) Recoveror(RECO) :: The Recoveror is used to resolve the distributed transaction in network
h) Dispatcher (Dnnn) :: The Dispatcher is useful in Multi Threaded Architecture
i) Lckn :: We can have upto 10 lock processes for inter instance locking in parallel sql.
How many types of Sql Statements are there in Oracle
There are basically 6 types of sql statments.They are
a) Data Definition Language(DDL) :: The DDL statements define and maintain objects and drop objects.
b) Data Manipulation Language(DML) :: The DML statements manipulate database data.
c) Transaction Control Statements :: Manage change by DML
d) Session Control :: Used to control the properties of current session enabling and disabling roles and changing .e.g. :: Alter Statements, Set Role
e) System Control Statements :: Change Properties of Oracle Instance .e.g.:: Alter System
f) Embedded Sql :: Incorporate DDL, DML and T.C.S in Programming Language.e.g:: Using the Sql Statements in languages such as 'C', Open, Fetch, execute and close
What is a Transaction in Oracle
A transaction is a Logical unit of work that compromises one or more SQL Statements executed by a single User. According to ANSI, a transaction begins with first executable statement and ends when it is explicitly committed or rolled back.

Key Words Used in Oracle
The Key words that are used in Oracle are ::
a) Committing :: A transaction is said to be committed when the transaction makes permanent changes resulting from the SQL statements.
b) Rollback :: A transaction that retracts any of the changes resulting from SQL statements in Transaction.
c) SavePoint :: For long transactions that contain many SQL statements, intermediate markers or savepoints are declared. Savepoints can be used to divide a transaction into smaller points.
d) Rolling Forward :: Process of applying redo log during recovery is called rolling forward.
e) Cursor :: A cursor is a handle ( name or a pointer) for the memory associated with a specific stamen. A cursor is basically an area allocated by Oracle for executing the Sql Statement. Oracle uses an implicit cursor statement for Single row query and Uses Explicit cursor for a multi row query.
f) System Global Area(SGA) :: The SGA is a shared memory region allocated by the Oracle that contains Data and control information for one Oracle Instance. It consists of Database Buffer Cache and Redo log Buffer.
g) Program Global Area (PGA) :: The PGA is a memory buffer that contains data and control information for server process.
g) Database Buffer Cache :: Database Buffer of SGA stores the most recently used blocks of database data. The set of database buffers in an instance is called Database Buffer Cache.
h) Redo log Buffer :: Redo log Buffer of SGA stores all the redo log entries.
i) Redo Log Files :: Redo log files are set of files that protect altered database data in memory that has not been written to Data Files. They are basically used for backup when a database crashes.
j) Process :: A Process is a 'thread of control' or mechanism in Operating System that executes series of steps.
What are Procedure, functions and Packages ?
Procedures and functions consist of set of PL/SQL statements that are grouped together as a unit to solve a specific problem or perform set of related tasks.
Procedures do not Return values while Functions return one One Value Packages :: Packages Provide a method of encapsulating and storing related procedures, functions, variables and other Package Contents
What are Database Triggers and Stored Procedures
Database Triggers :: Database Triggers are Procedures that are automatically executed as a result of insert in, update to, or delete from table.
Database triggers have the values old and new to denote the old value in the table before it is deleted and the new indicated the new value that will be used. DT are useful for implementing complex business rules which cannot be enforced using the integrity rules.We can have the trigger as Before trigger or After Trigger and at Statement or Row level. e.g:: operations insert,update ,delete 3 before ,after 3*2 A total of 6 combinatons
At statment level(once for the trigger) or row level( for every execution ) 6 * 2 A total of 12. Thus a total of 12 combinations are there and the restriction of usage of 12 triggers has been lifted from Oracle 7.3 Onwards.
Stored Procedures :: Stored Procedures are Procedures that are stored in Compiled form in the database.The advantage of using the stored procedures is that many users can use the same procedure in compiled and ready to use format.
How many Integrity Rules are there and what are they
There are Three Integrity Rules. They are as follows ::
a) Entity Integrity Rule :: The Entity Integrity Rule enforces that the Primary key cannot be Null
b) Foreign Key Integrity Rule :: The FKIR denotes that the relationship between the foreign key and the primary key has to be enforced.When there is data in Child Tables the Master tables cannot be deleted.
c) Business Integrity Rules :: The Third Intigrity rule is about the complex business processes which cannot be implemented by the above 2 rules.
What are the Various Master and Detail Relation ships.
The various Master and Detail Relationship are
a) NonIsolated :: The Master cannot be deleted when a child is exisiting
b) Isolated :: The Master can be deleted when the child is exisiting
c) Cascading :: The child gets deleted when the Master is deleted.
What are the Various Block Coordination Properties
The various Block Coordination Properties are
a) Immediate Default Setting. The Detail records are shown when the Master Record are shown.
b) Deffered with Auto Query Oracle Forms defer fetching the detail records until the operator navigates to the detail block.
c) Deffered with No Auto Query The operator must navigate to the detail block and explicitly execute a query
What are the Different Optimization Techniques
The Various Optimisation techniques are
a) Execute Plan :: we can see the plan of the query and change it accordingly based on the indexes
b) Optimizer_hint ::
set_item_property('DeptBlock',OPTIMIZER_HINT,'FIRST_ROWS');
Select /*+ First_Rows */ Deptno,Dname,Loc,Rowid from dept
where (Deptno > 25)
c) Optimize_Sql ::
By setting the Optimize_Sql = No, Oracle Forms assigns a single cursor for all SQL statements.This slow downs the processing because for evertime the SQL must be parsed whenver they are executed.
f45run module = my_firstform userid = scott/tiger optimize_sql = No
d) Optimize_Tp ::
By setting the Optimize_Tp= No, Oracle Forms assigns seperate cursor only for each query SELECT statement. All other SQL statements reuse the cursor.
f45run module = my_firstform userid = scott/tiger optimize_Tp = No
How does one change an Oracle user's password?(for DBA)
Issue the following SQL command:
ALTER USER <username> IDENTIFIED BY <new_password>;
From Oracle8 you can just type "password" from SQL*Plus, or if you need to change another user's password, type "password user_name". Look at this example:
SQL> password
Changing password for SCOTT
Old password:
New password:
Retype new password:
How does one create and drop database users?
Look at these examples:
CREATE USER scott
IDENTIFIED BY tiger -- Assign password
DEFAULT TABLESACE tools -- Assign space for table and index segments
TEMPORARY TABLESPACE temp; -- Assign sort space
DROP USER scott CASCADE; -- Remove user
After creating a new user, assign the required privileges:
GRANT CONNECT, RESOURCE TO scott;
GRANT DBA TO scott; -- Make user a DB Administrator
Remember to give the user some space quota on its tablespaces:
ALTER USER scott QUOTA UNLIMITED ON tools;
Who created all these users in my database?/ Can I drop this user? (for DBA)
Oracle creates a number of default database users or schemas when a new database is created. Below are a few of them:
SYS/CHANGE_ON_INSTALL or INTERNAL
Oracle Data Dictionary/ Catalog
Created by: ?/rdbms/admin/sql.bsq and various cat*.sql scripts
Can password be changed: Yes (Do so right after the database was created)
Can user be dropped: NO
SYSTEM/MANAGER
The default DBA user name (please do not use SYS)
Created by: ?/rdbms/admin/sql.bsq
Can password be changed: Yes (Do so right after the database was created)
Can user be dropped: NO
OUTLN/OUTLN
Stored outlines for optimizer plan stability
Created by: ?/rdbms/admin/sql.bsq
Can password be changed: Yes (Do so right after the database was created)
Can user be dropped: NO
SCOTT/TIGER, ADAMS/WOOD, JONES/STEEL, CLARK/CLOTH and BLAKE/PAPER.
Training/ demonstration users containing the popular EMP and DEPT tables
Created by: ?/rdbms/admin/utlsampl.sql
Can password be changed: Yes
Can user be dropped: YES - Drop users cascade from all production environments
HR/HR (Human Resources), OE/OE (Order Entry), SH/SH (Sales History).
Training/ demonstration users containing the popular EMPLOYEES and DEPARTMENTS tables
Created by: ?/demo/schema/mksample.sql
Can password be changed: Yes
Can user be dropped: YES - Drop users cascade from all production environments
CTXSYS/CTXSYS
Oracle interMedia (ConText Cartridge) administrator user
Created by: ?/ctx/admin/dr0csys.sql
TRACESVR/TRACE
Oracle Trace server
Created by: ?/rdbms/admin/otrcsvr.sql
DBSNMP/DBSNMP
Oracle Intelligent agent
Created by: ?/rdbms/admin/catsnmp.sql, called from catalog.sql
Can password be changed: Yes - put the new password in snmp_rw.ora file
Can user be dropped: YES - Only if you do not use the Intelligent Agents
ORDPLUGINS/ORDPLUGINS
Object Relational Data (ORD) User used by Time Series, etc.
Created by: ?/ord/admin/ordinst.sql
ORDSYS/ORDSYS
Object Relational Data (ORD) User used by Time Series, etc
Created by: ?/ord/admin/ordinst.sql
DSSYS/DSSYS
Oracle Dynamic Services and Syndication Server
Created by: ?/ds/sql/dssys_init.sql
MDSYS/MDSYS
Oracle Spatial administrator user
Created by: ?/ord/admin/ordinst.sql
AURORA$ORB$UNAUTHENTICATED/INVALID
Used for users who do not authenticate in Aurora/ORB
Created by: ?/javavm/install/init_orb.sql called from ?/javavm/install/initjvm.sql
PERFSTAT/PERFSTAT
Oracle Statistics Package (STATSPACK) that supersedes UTLBSTAT/UTLESTAT
Created by: ?/rdbms/admin/statscre.sql
Remember to change the passwords for the SYS and SYSTEM users immediately after installation!
Except for the user SYS, there should be no problem altering these users to use a different default and temporary tablespace.
How does one enforce strict password control? (for DBA)
By default Oracle's security is not extremely good. For example, Oracle will allow users to choose single character passwords and passwords that match their names and userids. Also, passwords don't ever expire. This means that one can hack an account for years without ever locking the user.
From Oracle8 one can manage passwords through profiles. Some of the things that one can restrict:
. FAILED_LOGIN_ATTEMPTS - failed login attempts before the account is locked
. PASSWORD_LIFE_TIME - limits the number of days the same password can be used for authentication
. PASSWORD_REUSE_TIME - number of days before a password can be reused
. PASSWORD_REUSE_MAX - number of password changes required before the current password can be reused
. PASSWORD_LOCK_TIME - number of days an account will be locked after maximum failed login attempts
. PASSWORD_GRACE_TIME - number of days after the grace period begins during which a warning is issued and login is allowed
. PASSWORD_VERIFY_FUNCTION - password complexity verification script
Look at this simple example:
CREATE PROFILE my_profile LIMIT
PASSWORD_LIFE_TIME 30;
ALTER USER scott PROFILE my_profile;
How does one switch to another user in Oracle? (for DBA)
Users normally use the "connect" statement to connect from one database user to another. However, DBAs can switch from one user to another without a password. Of course it is not advisable to bridge Oracle's security, but look at this example: SQL> select password from dba_users where username='SCOTT';
PASSWORD
F894844C34402B67
SQL> alter user scott identified by lion;
User altered.

SQL> connect scott/lion
Connected.

REM Do whatever you like...
SQL> connect system/manager
Connected.

SQL> alter user scott identified by values 'F894844C34402B67';
User altered.
SQL> connect scott/tiger
Connected.
Note: Also see the su.sql script in the Useful Scripts and Sample Programs Page.
What are snap shots and views
Snapshots are mirror or replicas of tables. Views are built using the columns from one or more tables. The Single Table View can be updated but the view with multi table cannot be updated
What are the OOPS concepts in Oracle.
Oracle does implement the OOPS concepts. The best example is the Property Classes. We can categorize the properties by setting the visual attributes and then attach the property classes for the objects. OOPS supports the concepts of objects and classes and we can consider the property classes as classes and the items as objects
What is the difference between candidate key, unique key and primary key
Candidate keys are the columns in the table that could be the primary keys and the primary key is the key that has been selected to identify the rows. Unique key is also useful for identifying the distinct rows in the table.)
What is concurrency
Concurrency is allowing simultaneous access of same data by different users. Locks useful for accesing the database are
a) Exclusive
The exclusive lock is useful for locking the row when an insert,update or delete is being done.This lock should not be applied when we do only select from the row.
b) Share lock
We can do the table as Share_Lock as many share_locks can be put on the same resource.
Previleges and Grants
Previleges are the right to execute a particulare type of SQL statements. e.g :: Right to Connect, Right to create, Right to resource Grants are given to the objects so that the object might be accessed accordingly.The grant has to be given by the owner of the object
Table Space,Data Files,Parameter File, Control Files
Table Space :: The table space is useful for storing the data in the database.When a database is created two table spaces are created.
a) System Table space :: This data file stores all the tables related to the system and dba tables
b) User Table space :: This data file stores all the user related tables
We should have seperate table spaces for storing the tables and indexes so that the access is fast.
Data Files :: Every Oracle Data Base has one or more physical data files.They store the data for the database.Every datafile is associated with only one database.Once the Data file is created the size cannot change.To increase the size of the database to store more data we have to add data file.
Parameter Files :: Parameter file is needed to start an instance.A parameter file contains the list of instance configuration parameters e.g.::
db_block_buffers = 500
db_name = ORA7
db_domain = u.s.acme lang
Control Files :: Control files record the physical structure of the data files and redo log files
They contain the Db name, name and location of dbs, data files ,redo log files and time stamp.
Physical Storage of the Data
The finest level of granularity of the data base are the data blocks.
Data Block :: One Data Block correspond to specific number of physical database space
Extent :: Extent is the number of specific number of contigious data blocks.
Segments :: Set of Extents allocated for Extents. There are three types of Segments
a) Data Segment :: Non Clustered Table has data segment data of every table is stored in cluster data segment
b) Index Segment :: Each Index has index segment that stores data
c) Roll Back Segment :: Temporarily store 'undo' information
What are the Pct Free and Pct Used
Pct Free is used to denote the percentage of the free space that is to be left when creating a table. Similarly Pct Used is used to denote the percentage of the used space that is to be used when creating a table
eg.:: Pctfree 20, Pctused 40
What is Row Chaining
The data of a row in a table may not be able to fit the same data block.Data for row is stored in a chain of data blocks .
What is a 2 Phase Commit
Two Phase commit is used in distributed data base systems. This is useful to maintain the integrity of the database so that all the users see the same values. It contains DML statements or Remote Procedural calls that reference a remote object. There are basically 2 phases in a 2 phase commit.
a) Prepare Phase :: Global coordinator asks participants to prepare
b) Commit Phase :: Commit all participants to coordinator to Prepared, Read only or abort Reply
What is the difference between deleting and truncating of tables
Deleting a table will not remove the rows from the table but entry is there in the database dictionary and it can be retrieved But truncating a table deletes it completely and it cannot be retrieved.
What are mutating tables
When a table is in state of transition it is said to be mutating. eg :: If a row has been deleted then the table is said to be mutating and no operations can be done on the table except select.
What are Codd Rules
Codd Rules describe the ideal nature of a RDBMS. No RDBMS satisfies all the 12 codd rules and Oracle Satisfies 11 of the 12 rules and is the only Rdbms to satisfy the maximum number of rules.
What is Normalisation
Normalisation is the process of organising the tables to remove the redundancy.There are mainly 5 Normalisation rules.
a) 1 Normal Form :: A table is said to be in 1st Normal Form when the attributes are atomic
b) 2 Normal Form :: A table is said to be in 2nd Normal Form when all the candidate keys are dependant on the primary key
c) 3rd Normal Form :: A table is said to be third Normal form when it is not dependant transitively
What is the Difference between a post query and a pre query
A post query will fire for every row that is fetched but the pre query will fire only once.
Deleting the Duplicate rows in the table
We can delete the duplicate rows in the table by using the Rowid
Can U disable database trigger? How?
Yes. With respect to table
ALTER TABLE TABLE
[[ DISABLE all_trigger ]]
What is pseudo columns ? Name them?
A pseudocolumn behaves like a table column, but is not actually stored in the table. You can select from pseudocolumns, but you cannot insert, update, or delete their values. This section describes these pseudocolumns:
* CURRVAL
* NEXTVAL
* LEVEL
* ROWID
* ROWNUM
How many columns can table have?
The number of columns in a table can range from 1 to 254.

Is space acquired in blocks or extents ?
In extents .
What is clustered index?
In an indexed cluster, rows are stored together based on their cluster key values . Can not applied for HASH.
What are the datatypes supported By oracle (INTERNAL)?
Varchar2, Number,Char , MLSLABEL.
What are attributes of cursor?
%FOUND , %NOTFOUND , %ISOPEN,%ROWCOUNT
Can you use select in FROM clause of SQL select ?
Yes.
Which trigger are created when master -detail relay?
master delete property
* NON-ISOLATED (default)
a) on check delete master
b) on clear details
c) on populate details
* ISOLATED
a) on clear details
b) on populate details
* CASCADE
a) per-delete
b) on clear details
c) on populate details
which system variables can be set by users?
SYSTEM.MESSAGE_LEVEL
SYSTEM.DATE_THRESHOLD
SYSTEM.EFFECTIVE_DATE
SYSTEM.SUPPRESS_WORKING
What are object group?
An object group is a container for a group of objects. You define an object group when you want to package related objects so you can copy or reference them in another module.
What are referenced objects?
Referencing allows you to create objects that inherit their functionality and appearance from other objects. Referencing an object is similar to copying an object, except that the resulting reference object maintains a link to its source object. A reference object automatically inherits any changes that have been made to the source object when you open or regenerate the module that contains the reference object.
Can you store objects in library?
Referencing allows you to create objects that inherit their functionality and appearance from other objects. Referencing an object is similar to copying an object, except that the resulting reference object maintains a link to its source object. A reference object automatically inherits any changes that have been made to the source object when you open or regenerate the module that contains the reference object.
Is forms 4.5 object oriented tool ? why?
yes , partially. 1) PROPERTY CLASS - inheritance property 2) OVERLOADING : procedures and functions.
Can you issue DDL in forms?
yes, but you have to use FORMS_DDL.
Referencing allows you to create objects that inherit their functionality and appearance from other objects. Referencing an object is similar to copying an object, except that the resulting reference object maintains a link to its source object. A reference object automatically inherits any changes that have been made to the source object when you open or regenerate the module that contains the reference object. Any string expression up to 32K:
- a literal
- an expression or a variable representing the text of a block of dynamically created PL/SQL code
- a DML statement or
- a DDL statement
Restrictions:
The statement you pass to FORMS_DDL may not contain bind variable references in the string, but the values of bind variables can be concatenated into the string before passing the result to FORMS_DDL.

What is SECURE property?
- Hides characters that the operator types into the text item. This setting is typically used for password protection.
What are the types of triggers and how the sequence of firing in text item
Triggers can be classified as Key Triggers, Mouse Triggers ,Navigational Triggers.
Key Triggers :: Key Triggers are fired as a result of Key action.e.g :: Key-next-field, Key-up,Key-Down
Mouse Triggers :: Mouse Triggers are fired as a result of the mouse navigation.e.g. When-mouse-button-presed,when-mouse-doubleclicked,etc
Navigational Triggers :: These Triggers are fired as a result of Navigation. E.g. : Post-Text-item,Pre-text-item.
We also have event triggers like when ?new-form-instance and when-new-block-instance.
We cannot call restricted procedures like go_to(?my_block.first_item?) in the Navigational triggers
But can use them in the Key-next-item.
The Difference between Key-next and Post-Text is an very important question. The key-next is fired as a result of the key action while the post text is fired as a result of the mouse movement. Key next will not fire unless there is a key event. The sequence of firing in a text item are as follows ::
a) pre - text
b) when new item
c) key-next
d) when validate
e) post text
Can you store pictures in database? How?
Yes , in long Raw datatype.
What are property classes ? Can property classes have trigger?
Property class inheritance is a powerful feature that allows you to quickly define objects that conform to your own interface and functionality standards. Property classes also allow you to make global changes to applications quickly. By simply changing the definition of a property class, you can change the definition of all objects that inherit properties from that class.
Yes . All type of triggers .
If you have property class attached to an item and you have same trigger written for the item . Which will fire first?
Item level trigger fires , If item level trigger fires, property level trigger won't fire. Triggers at the lowest level are always given the first preference. The item level trigger fires first and then the block and then the Form level trigger.
What are record groups ? * Can record groups created at run-time?
A record group is an internal Oracle Forms data structure that has a column/row framework similar to a database table. However, unlike database tables, record groups are separate objects that belong to the form module in which they are defined. A record group can have an unlimited number of columns of type CHAR, LONG, NUMBER, or DATE provided that the total number of columns does not exceed 64K. Record group column names cannot exceed 30 characters.
Programmatically, record groups can be used whenever the functionality offered by a two-dimensional array of multiple data types is desirable.
TYPES OF RECORD GROUP:
Query Record Group A query record group is a record group that has an associated SELECT statement. The columns in a query record group derive their default names, data types, and lengths from the database columns referenced in the SELECT statement. The records in a query record group are the rows retrieved by the query associated with that record group.
Non-query Record Group A non-query record group is a group that does not have an associated query, but whose structure and values can be modified programmatically at runtime.
Static Record Group A static record group is not associated with a query; rather, you define its structure and row values at design time, and they remain fixed at runtime.
What are ALERT?
An ALERT is a modal window that displays a message notifying operator of some application condition.

Can a button have icon and label at the same time ?
-NO

What is mouse navigate property of button?
When Mouse Navigate is True (the default), Oracle Forms performs standard navigation to move the focus to the item when the operator activates the item with the mouse.
When Mouse Navigate is set to False, Oracle Forms does not perform navigation (and the resulting validation) to move to the item when an operator activates the item with the mouse.
What is FORMS_MDI_WINDOW?
forms run inside the MDI application window. This property is useful for calling a form from another one.
What are timers ? when when-timer-expired does not fire?
The When-Timer-Expired trigger can not fire during trigger, navigation, or transaction processing.
Can object group have a block?
Yes , object group can have block as well as program units.
How many types of canvases are there.
There are 2 types of canvases called as Content and Stack Canvas. Content canvas is the default and the one that is used mostly for giving the base effect. Its like a plate on which we add items and stacked canvas is used for giving 3 dimensional effect.
What are user-exits?
It invokes 3GL programs.

Can you pass values to-and-fro from foreign function ? how ?
Yes . You obtain a return value from a foreign function by assigning the return value to an Oracle Forms variable or item. Make sure that the Oracle Forms variable or item is the same data type as the return value from the foreign function.
After assigning an Oracle Forms variable or item value to a PL/SQL variable, pass the PL/SQL variable as a parameter value in the PL/SQL interface of the foreign function. The PL/SQL variable that is passed as a parameter must be a valid PL/SQL data type; it must also be the appropriate parameter type as defined in the PL/SQL interface.
What is IAPXTB structure ?
The entries of Pro * C and user exits and the form which simulate the proc or user_exit are stored in IAPXTB table in d/b.
Can you call WIN-SDK thru user exits?
YES.
Does user exits supports DLL on MSWINDOWS ?
YES .

What is path setting for DLL?
Make sure you include the name of the DLL in the FORMS45_USEREXIT variable of the ORACLE.INI file, or rename the DLL to F45XTB.DLL. If you rename the DLL to F45XTB.DLL, replace the existing F45XTB.DLL in the ORAWINBIN directory with the new F45XTB.DLL.
How is mapping of name of DLL and function done?
The dll can be created using the Visual C++ / Visual Basic Tools and then the dll is put in the path that is defined the registry.
What is precompiler?
It is similar to C precompiler directives.
Can you connect to non - oracle datasource ?
Yes .
What are key-mode and locking mode properties? level ?
Key Mode : Specifies how oracle forms uniquely identifies rows in the database.This is property includes for application that will run against NON-ORACLE datasources .
Key setting unique (default.)
dateable
n-updateable.

Locking mode :
Specifies when Oracle Forms should attempt to obtain database locks on rows that correspond to queried records in the form. a) immediate b) delayed
What are savepoint mode and cursor mode properties ? level?
Specifies whether Oracle Forms should issue savepoints during a session. This property is included primarily for applications that will run against non-ORACLE data sources. For applications that will run against ORACLE, use the default setting.
Cursor mode - define cursor state across transaction Open/close.
What is transactional trigger property?
Identifies a block as transactional control block. i.e. non - database block that oracle forms should manage as transactional block.(NON-ORACLE datasource) default - FALSE.
What is OLE automation ?
OLE automation allows an OLE server application to expose a set of commands and functions that can be invoked from an OLE container application. OLE automation provides a way for an OLE container application to use the features of an OLE server application to manipulate an OLE object from the OLE container environment. (FORMS_OLE)
What does invoke built-in do?
This procedure invokes a method.
Syntax:
PROCEDURE OLE2.INVOKE
(object obj_type,
method VARCHAR2,
list list_type := 0);
Parameters:
object Is an OLE2 Automation Object.
method Is a method (procedure) of the OLE2 object.
list Is the name of an argument list assigned to the OLE2.CREATE_ARGLIST function.
What are OPEN_FORM,CALL_FORM,NEW_FORM? diff?
CALL_FORM : It calls the other form. but parent remains active, when called form completes the operation , it releases lock and control goes back to the calling form.
When you call a form, Oracle Forms issues a savepoint for the called form. If the CLEAR_FORM function causes a rollback when the called form is current, Oracle Forms rolls back uncommitted changes to this savepoint.
OPEN_FORM : When you call a form, Oracle Forms issues a savepoint for the called form. If the CLEAR_FORM function causes a rollback when the called form is current, Oracle Forms rolls back uncommitted changes to this savepoint.
NEW_FORM : Exits the current form and enters the indicated form. The calling form is terminated as the parent form. If the calling form had been called by a higher form, Oracle Forms keeps the higher call active and treats it as a call to the new form. Oracle Forms releases memory (such as database cursors) that the terminated form was using.
Oracle Forms runs the new form with the same Runform options as the parent form. If the parent form was a called form, Oracle Forms runs the new form with the same options as the parent form.
What is call form stack?
When successive forms are loaded via the CALL_FORM procedure, the resulting module hierarchy is known as the call form stack.
Can u port applictions across the platforms? how?
Yes we can port applications across platforms.Consider the form developed in a windows system.The form would be generated in unix system by using f45gen my_form.fmb scott/tiger
What is a visual attribute?
Visual attributes are the font, color, and pattern properties that you set for form and menu objects that appear in your application's interface.
Diff. between VAT and Property Class?
Named visual attributes define only font, color, and pattern attributes; property classes can contain these and any other properties.
You can change the appearance of objects at runtime by changing the named visual attribute programmatically; property class assignment cannot be changed programmatically. When an object is inheriting from both a property class and a named visual attribute, the named visual attribute settings take precedence, and any visual attribute properties in the class are ignored.
Which trigger related to mouse?
When-Mouse-Click
When-Mouse-DoubleClick
When-Mouse-Down
When-Mouse-Enter
When-Mouse-Leave
When-Mouse-Move
When-Mouse-Up
What is Current record attribute property?
Specifies the named visual attribute used when an item is part of the current record. Current Record Attribute is frequently used at the block level to display the current row in a multi-record If you define an item-level Current Record Attribute, you can display a pre-determined item in a special color when it is part of the current record, but you cannot dynamically highlight the current item, as the input focus changes.
Can u change VAT at run time?
Yes. You can programmatically change an object's named visual attribute setting to change the font, color, and pattern of the object at runtime.
Can u set default font in forms?
Yes. Change windows registry(regedit). Set form45_font to the desired font.
_break
What is Log Switch ?
The point at which ORACLE ends writing to one online redo log file and begins writing to another is called a log switch.
What is On-line Redo Log?
The On-line Redo Log is a set of tow or more on-line redo files that record all committed changes made to the database. Whenever a transaction is committed, the corresponding redo entries temporarily stores in redo log buffers of the SGA are written to an on-line redo log file by the background process LGWR. The on-line redo log files are used in cyclical fashion.
Which parameter specified in the DEFAULT STORAGE clause of CREATE TABLESPACE cannot be altered after creating the tablespace?
All the default storage parameters defined for the tablespace can be changed using the ALTER TABLESPACE command. When objects are created their INITIAL and MINEXTENS values cannot be changed.

What are the steps involved in Database Startup ?
Start an instance, Mount the Database and Open the Database.
Rolling forward to recover data that has not been recorded in data files, yet has been recorded in the on-line redo log, including the contents of rollback segments. Rolling back transactions that have been explicitly rolled back or have not been committed as indicated by the rollback segments regenerated in step a. Releasing any resources (locks) held by transactions in process at the time of the failure. Resolving any pending distributed transactions undergoing a two-phase commit at the time of the instance failure.
Can Full Backup be performed when the database is open ?
No.

What are the different modes of mounting a Database with the Parallel Server ?
Exclusive Mode If the first instance that mounts a database does so in exclusive mode, only that Instance can mount the database.
Parallel Mode If the first instance that mounts a database is started in parallel mode, other instances that are started in parallel mode can also mount the database.
What are the advantages of operating a database in ARCHIVELOG mode over operating it in NO ARCHIVELOG mode ?
Complete database recovery from disk failure is possible only in ARCHIVELOG mode. Online database backup is possible only in ARCHIVELOG mode.
What are the steps involved in Database Shutdown ?
Close the Database, Dismount the Database and Shutdown the Instance.
What is Archived Redo Log ?
Archived Redo Log consists of Redo Log files that have archived before being reused.

What is Restricted Mode of Instance Startup ?
An instance can be started in (or later altered to be in) restricted mode so that when the database is open connections are limited only to those whose user accounts have been granted the RESTRICTED SESSION system privilege.
Can u have OLE objects in forms?
Yes.
Can u have VBX and OCX controls in forms ?
Yes.
What r the types of windows (Window style)?
Specifies whether the window is a Document window or a Dialog window.
What is OLE Activation style property?
Specifies the event that will activate the OLE containing item.
Can u change the mouse pointer ? How?
Yes. Specifies the mouse cursor style. Use this property to dynamically change the shape of the cursor.
How many types of columns are there and what are they
Formula columns :: For doing mathematical calculations and returning one value Summary Columns :: For doing summary calculations such as summations etc. Place holder Columns :: These columns are useful for storing the value in a variable

Can u have more than one layout in report
It is possible to have more than one layout in a report by using the additional layout option in the layout editor.
Can u run the report with out a parameter form
Yes it is possible to run the report without parameter form by setting the PARAM value to Null
What is the lock option in reports layout
By using the lock option we cannot move the fields in the layout editor outside the frame. This is useful for maintaining the fields .
What is Flex
Flex is the property of moving the related fields together by setting the flex property on
What are the minimum number of groups required for a matrix report
The minimum of groups required for a matrix report are 4 e -----
What is a Synonym ?
A synonym is an alias for a table, view, sequence or program unit.
What is a Sequence ?
A sequence generates a serial list of unique numbers for numerical columns of a database's tables.
What is a Segment ?
A segment is a set of extents allocated for a certain logical structure.
What is schema?
A schema is collection of database objects of a User.
Describe Referential Integrity ?
A rule defined on a column (or set of columns) in one table that allows the insert or update of a row only if the value for the column or set of columns (the dependent value) matches a value in a column of a related table (the referenced value). It also specifies the type of data manipulation allowed on referenced data and the action to be performed on dependent data as a result of any action on referenced data.
What is Hash Cluster ?
A row is stored in a hash cluster based on the result of applying a hash function to the row's cluster key value. All rows with the same hash key value are stores together on disk.
What is a Private Synonyms ?
A Private Synonyms can be accessed only by the owner.
What is Database Link ?
A database link is a named object that describes a "path" from one database to another.
What is index cluster?
A cluster with an index on the cluster key.
What is hash cluster?
A row is stored in a hash cluster based on the result of applying a hash function to the row's cluster key value. All rows with the same hash key value are stores together on disk.
When can hash cluster used?
Hash clusters are better choice when a table is often queried with equality queries. For such queries the specified cluster key value is hashed. The resulting hash key value points directly to the area on disk that stores the specified rows.
When can hash cluster used?
Hash clusters are better choice when a table is often queried with equality queries. For such queries the specified cluster key value is hashed. The resulting hash key value points directly to the area on disk that stores the specified rows.

What are the types of database links?
Private database link, public database link & network database link.
What is private database link?
Private database link is created on behalf of a specific user. A private database link can be used only when the owner of the link specifies a global object name in a SQL statement or in the definition of the owner's views or procedures.
What is public database link?
Public database link is created for the special user group PUBLIC. A public database link can be used when any user in the associated database specifies a global object name in a SQL statement or object definition.
What is network database link?
Network database link is created and managed by a network domain service. A network database link can be used when any user of any database in the network specifies a global object name in a SQL statement or object definition.
What is data block?
Oracle database's data is stored in data blocks. One data block corresponds to a specific number of bytes of physical database space on disk.
How to define data block size?
A data block size is specified for each Oracle database when the database is created. A database users and allocated free database space in Oracle data blocks. Block size is specified in init.ora file and cannot be changed latter.
What is row chaining?
In circumstances, all of the data for a row in a table may not be able to fit in the same data block. When this occurs, the data for the row is stored in a chain of data block (one or more) reserved for that segment.

What is an extent?
An extent is a specific number of contiguous data blocks, obtained in a single allocation and used to store a specific type of information.
What are the different types of segments?
Data segment, index segment, rollback segment and temporary segment.
What is a data segment?
Each non-clustered table has a data segment. All of the table's data is stored in the extents of its data segment. Each cluster has a data segment. The data of every table in the cluster is stored in the cluster's data segment.
What is an index segment?
Each index has an index segment that stores all of its data.
What is rollback segment?
A database contains one or more rollback segments to temporarily store "undo" information.
What are the uses of rollback segment?
To generate read-consistent database information during database recovery and to rollback uncommitted transactions by the users.
What is a temporary segment?
Temporary segments are created by Oracle when a SQL statement needs a temporary work area to complete execution. When the statement finishes execution, the temporary segment extents are released to the system for future use.
What is a datafile?
Every Oracle database has one or more physical data files. A database's data files contain all the database data. The data of logical database structures such as tables and indexes is physically stored in the data files allocated for a database.
What are the characteristics of data files?
A data file can be associated with only one database. Once created a data file can't change size. One or more data files form a logical unit of database storage called a tablespace.
What is a redo log?
The set of redo log files for a database is collectively known as the database redo log.

What is the function of redo log?
The primary function of the redo log is to record all changes made to data.
What is the use of redo log information?
The information in a redo log file is used only to recover the database from a system or media failure prevents database data from being written to a database's data files.

What does a control file contains?
- Database name
- Names and locations of a database's files and redolog files.
- Time stamp of database creation.

What is the use of control file?
When an instance of an Oracle database is started, its control file is used to identify the database and redo log files that must be opened for database operation to proceed. It is also used in database recovery.
Is it possible to split the print reviewer into more than one region?
Yes
Is it possible to center an object horizontally in a repeating frame that has a variable horizontal size?
Yes
For a field in a repeating frame, can the source come from the column which does not exist in the data group which forms the base for the frame?
Yes
Can a field be used in a report without it appearing in any data group?
Yes
The join defined by the default data link is an outer join yes or no?
Yes
Can a formula column referred to columns in higher group?
Yes
Can a formula column be obtained through a select statement?
Yes
Is it possible to insert comments into sql statements return in the data model editor?
Yes
Is it possible to disable the parameter from while running the report?
Yes
When a form is invoked with call_form, Does oracle forms issues a save point?
Yes
Explain the difference between a hot backup and a cold backup and the benefits associated with each.
A hot backup is basically taking a backup of the database while it is still up and running and it must be in archive log mode. A cold backup is taking a backup of the database while it is shut down and does not require being in archive log mode. The benefit of taking a hot backup is that the database is still available for use while the backup is occurring and you can recover the database to any point in time. The benefit of taking a cold backup is that it is typically easier to administer the backup and recovery process. In addition, since you are taking cold backups the database does not require being in archive log mode and thus there will be a slight performance gain as the database is not cutting archive logs to disk.
You have just had to restore from backup and do not have any control files. How would you go about bringing up this database?
I would create a text based backup control file, stipulating where on disk all the data files where and then issue the recover command with the using backup control file clause.

How do you switch from an init.ora file to a spfile?
Issue the create spfile from pfile command.

Explain the difference between a data block, an extent and a segment.
A data block is the smallest unit of logical storage for a database object. As objects grow they take chunks of additional storage that are composed of contiguous data blocks. These groupings of contiguous data blocks are called extents. All the extents that an object takes when grouped together are considered the segment of the database object.
Give two examples of how you might determine the structure of the table DEPT.
Use the describe command or use the dbms_metadata.get_ddl package.
Where would you look for errors from the database engine?
In the alert log.
Compare and contrast TRUNCATE and DELETE for a table.
Both the truncate and delete command have the desired outcome of getting rid of all the rows in a table. The difference between the two is that the truncate command is a DDL operation and just moves the high water mark and produces a now rollback. The delete command, on the other hand, is a DML operation, which will produce a rollback and thus take longer to complete.
Give the reasoning behind using an index.
Faster access to data blocks in a table.
Give the two types of tables involved in producing a star schema and the type of data they hold.
Fact tables and dimension tables. A fact table contains measurements while dimension tables will contain data that will help describe the fact tables.
What type of index should you use on a fact table?
A Bitmap index.

Give two examples of referential integrity constraints.
A primary key and a foreign key.
A table is classified as a parent table and you want to drop and re-create it. How would you do this without affecting the children tables?
Disable the foreign key constraint to the parent, drop the table, re-create the table, enable the foreign key constraint.
Explain the difference between ARCHIVELOG mode and NOARCHIVELOG mode and the benefits and disadvantages to each.
ARCHIVELOG mode is a mode that you can put the database in for creating a backup of all transactions that have occurred in the database so that you can recover to any point in time. NOARCHIVELOG mode is basically the absence of ARCHIVELOG mode and has the disadvantage of not being able to recover to any point in time. NOARCHIVELOG mode does have the advantage of not having to write transactions to an archive log and thus increases the performance of the database slightly.
What command would you use to create a backup control file?
Alter database backup control file to trace.
Give the stages of instance startup to a usable state where normal users may access it.
STARTUP NOMOUNT - Instance startup
STARTUP MOUNT - The database is mounted
STARTUP OPEN - The database is opened

What column differentiates the V$ views to the GV$ views and how?
The INST_ID column which indicates the instance in a RAC environment the information came from.
How would you go about generating an EXPLAIN plan?
Create a plan table with utlxplan.sql.
Use the explain plan set statement_id = 'tst1' into plan_table for a SQL statement
Look at the explain plan with utlxplp.sql or utlxpls.sql

How would you go about increasing the buffer cache hit ratio?
Use the buffer cache advisory over a given workload and then query the v$db_cache_advice table. If a change was necessary then I would use the alter system set db_cache_size command.

Explain an ORA-01555
You get this error when you get a snapshot too old within rollback. It can usually be solved by increasing the undo retention or increasing the size of rollbacks. You should also look at the logic involved in the application getting the error message.
Explain the difference between $ORACLE_HOME and $ORACLE_BASE.
ORACLE_BASE is the root directory for oracle. ORACLE_HOME located beneath ORACLE_BASE is where the oracle products reside.
How would you determine the time zone under which a database was operating?
select DBTIMEZONE from dual;
Explain the use of setting GLOBAL_NAMES equal to TRUE.
Setting GLOBAL_NAMES dictates how you might connect to a database. This variable is either TRUE or FALSE and if it is set to TRUE it enforces database links to have the same name as the remote database to which they are linking.

What command would you use to encrypt a PL/SQL application?
WRAP

Explain the difference between a FUNCTION, PROCEDURE and PACKAGE.
A function and procedure are the same in that they are intended to be a collection of PL/SQL code that carries a single task. While a procedure does not have to return any values to the calling application, a function will return a single value. A package on the other hand is a collection of functions and procedures that are grouped together based on their commonality to a business function or application.
Explain the use of table functions.
Table functions are designed to return a set of rows through PL/SQL logic but are intended to be used as a normal table or view in a SQL statement. They are also used to pipeline information in an ETL process.
Name three advisory statistics you can collect.
Buffer Cache Advice, Segment Level Statistics, & Timed Statistics
Where in the Oracle directory tree structure are audit traces placed?
In unix $ORACLE_HOME/rdbms/audit, in Windows the event viewer
Explain materialized views and how they are used.
Materialized views are objects that are reduced sets of information that have been summarized, grouped, or aggregated from base tables. They are typically used in data warehouse or decision support systems.
When a user process fails, what background process cleans up after it?
PMON

What background process refreshes materialized views?
The Job Queue Processes.
How would you determine what sessions are connected and what resources they are waiting for?
Use of V$SESSION and V$SESSION_WAIT
Describe what redo logs are.
Redo logs are logical and physical structures that are designed to hold all the changes made to a database and are intended to aid in the recovery of a database.

How would you force a log switch?
ALTER SYSTEM SWITCH LOGFILE;
Give two methods you could use to determine what DDL changes have been made.
You could use Logminer or Streams

What does coalescing a tablespace do?
Coalescing is only valid for dictionary-managed tablespaces and de-fragments space by combining neighboring free extents into large single extents.
What is the difference between a TEMPORARY tablespace and a PERMANENT tablespace?
A temporary tablespace is used for temporary objects such as sort structures while permanent tablespaces are used to store those objects meant to be used as the true objects of the database.
Name a tablespace automatically created when you create a database.
The SYSTEM tablespace.
When creating a user, what permissions must you grant to allow them to connect to the database?
Grant the CONNECT to the user.
How do you add a data file to a tablespace
ALTER TABLESPACE <tablespace_name> ADD DATAFILE <datafile_name> SIZE
How do you resize a data file?
ALTER DATABASE DATAFILE <datafile_name> RESIZE <new_size>;
What view would you use to look at the size of a data file?
DBA_DATA_FILES
What view would you use to determine free space in a tablespace?
DBA_FREE_SPACE
How would you determine who has added a row to a table?
Turn on fine grain auditing for the table.
How can you rebuild an index?
ALTER INDEX <index_name> REBUILD;
Explain what partitioning is and what its benefit is.
Partitioning is a method of taking large tables and indexes and splitting them into smaller, more manageable pieces.
You have just compiled a PL/SQL package but got errors, how would you view the errors?
SHOW ERRORS
How can you gather statistics on a table?
The ANALYZE command.

How can you enable a trace for a session?
Use the DBMS_SESSION.SET_SQL_TRACE or
Use ALTER SESSION SET SQL_TRACE = TRUE;
What is the difference between the SQL*Loader and IMPORT utilities?
These two Oracle utilities are used for loading data into the database. The difference is that the import utility relies on the data being produced by another Oracle utility EXPORT while the SQL*Loader utility allows data to be loaded that has been produced by other utilities from different data sources just so long as it conforms to ASCII formatted or delimited files.
Name two files used for network connection to a database.
TNSNAMES.ORA and SQLNET.ORA
What is the function of Optimizer ?
The goal of the optimizer is to choose the most efficient way to execute a SQL statement.
What is Execution Plan ?
The combinations of the steps the optimizer chooses to execute a statement is called an execution plan.
Can one resize tablespaces and data files? (for DBA)
One can manually increase or decrease the size of a datafile from Oracle 7.2 using the command.
ALTER DATABASE DATAFILE 'filename2' RESIZE 100M;
Because you can change the sizes of datafiles, you can add more space to your database without adding more datafiles. This is beneficial if you are concerned about reaching the maximum number of datafiles allowed in your database.
Manually reducing the sizes of datafiles allows you to reclaim unused space in the database. This is useful for correcting errors in estimations of space requirements.
Also, datafiles can be allowed to automatically extend if more space is required. Look at the following command:
CREATE TABLESPACE pcs_data_ts
DATAFILE 'c:\ora_apps\pcs\pcsdata1.dbf' SIZE 3M
AUTOEXTEND ON NEXT 1M MAXSIZE UNLIMITED
DEFAULT STORAGE (INITIAL 10240
NEXT 10240
MINEXTENTS 1
MAXEXTENTS UNLIMITED
PCTINCREASE 0)
ONLINE
PERMANENT;
What is SAVE POINT ?
For long transactions that contain many SQL statements, intermediate markers or savepoints can be declared which can be used to divide a transaction into smaller parts. This allows the option of later rolling back all work performed from the current point in the transaction to a declared savepoint within the transaction.

What are the values that can be specified for OPTIMIZER MODE Parameter ?
COST and RULE.
Can one rename a tablespace? (for DBA)
No, this is listed as Enhancement Request 148742. Workaround:
Export all of the objects from the tablespace
Drop the tablespace including contents
Recreate the tablespace
Import the objects

What is RULE-based approach to optimization ?
Choosing an executing planbased on the access paths available and the ranks of these access paths.
What are the values that can be specified for OPTIMIZER_GOAL parameter of the ALTER SESSION Command ?
CHOOSE,ALL_ROWS,FIRST_ROWS and RULE.
How does one create a standby database? (for DBA)
While your production database is running, take an (image copy) backup and restore it on duplicate hardware. Note that an export will not work!!!
On your standby database, issue the following commands:
ALTER DATABASE CREATE STANDBY CONTROLFILE AS 'filename';
ALTER DATABASE MOUNT STANDBY DATABASE;
RECOVER STANDBY DATABASE;
On systems prior to Oracle 8i, write a job to copy archived redo log files from the primary database to the standby system, and apply the redo log files to the standby database (pipe it). Remember the database is recovering and will prompt you for the next log file to apply.
Oracle 8i onwards provide an "Automated Standby Database" feature, which will send archived, log files to the remote site via NET8, and apply then to the standby database.
When one needs to activate the standby database, stop the recovery process and activate it:
ALTER DATABASE ACTIVATE STANDBY DATABASE;

How does one give developers access to trace files (required as input to tkprof)? (for DBA)
The "alter session set sql_trace=true" command generates trace files in USER_DUMP_DEST that can be used by developers as input to tkprof. On Unix the default file mask for these files are "rwx r-- ---".
There is an undocumented INIT.ORA parameter that will allow everyone to read (rwx r-r--) these trace files:
_trace_files_public = true
Include this in your INIT.ORA file and bounce your database for it to take effect.
What are the responsibilities of a Database Administrator ?
Installing and upgrading the Oracle Server and application tools. Allocating system storage and planning future storage requirements for the database system. Managing primary database structures (tablespaces) Managing primary objects (table,views,indexes) Enrolling users and maintaining system security. Ensuring compliance with Oralce license agreement Controlling and monitoring user access to the database. Monitoring and optimizing the performance of the database. Planning for backup and recovery of database information. Maintain archived data on tape Backing up and restoring the database. Contacting Oracle Corporation for technical support.
What is a trace file and how is it created ?
Each server and background process can write an associated trace file. When an internal error is detected by a process or user process, it dumps information about the error to its trace. This can be used for tuning the database.
What are the roles and user accounts created automatically with the database?
DBA - role Contains all database system privileges.
SYS user account - The DBA role will be assigned to this account. All of the base tables and views for the database's dictionary are store in this schema and are manipulated only by ORACLE. SYSTEM user account - It has all the system privileges for the database and additional tables and views that display administrative information and internal tables and views used by oracle tools are created using this username.
What are the minimum parameters should exist in the parameter file (init.ora) ?
DB NAME - Must set to a text string of no more than 8 characters and it will be stored inside the datafiles, redo log files and control files and control file while database creation.
DB_DOMAIN - It is string that specifies the network domain where the database is created. The global database name is identified by setting these parameters
(DB_NAME & DB_DOMAIN) CONTORL FILES - List of control filenames of the database. If name is not mentioned then default name will be used.
DB_BLOCK_BUFFERS - To determine the no of buffers in the buffer cache in SGA.
PROCESSES - To determine number of operating system processes that can be connected to ORACLE concurrently. The value should be 5 (background process) and additional 1 for each user.
ROLLBACK_SEGMENTS - List of rollback segments an ORACLE instance acquires at database startup. Also optionally LICENSE_MAX_SESSIONS,LICENSE_SESSION_WARNING and LICENSE_MAX_USERS.
Why and when should I backup my database? (for DBA)
Backup and recovery is one of the most important aspects of a DBAs job. If you lose your company's data, you could very well lose your job. Hardware and software can always be replaced, but your data may be irreplaceable!
Normally one would schedule a hierarchy of daily, weekly and monthly backups, however consult with your users before deciding on a backup schedule. Backup frequency normally depends on the following factors:
. Rate of data change/ transaction rate
. Database availability/ Can you shutdown for cold backups?
. Criticality of the data/ Value of the data to the company
. Read-only tablespace needs backing up just once right after you make it read-only
. If you are running in archivelog mode you can backup parts of a database over an extended cycle of days
. If archive logging is enabled one needs to backup archived log files timeously to prevent database freezes
. Etc.
Carefully plan backup retention periods. Ensure enough backup media (tapes) are available and that old backups are expired in-time to make media available for new backups. Off-site vaulting is also highly recommended.
Frequently test your ability to recover and document all possible scenarios. Remember, it's the little things that will get you. Most failed recoveries are a result of organizational errors and miscommunications.
What strategies are available for backing-up an Oracle database? (for DBA)
The following methods are valid for backing-up an Oracle database:
Export/Import - Exports are "logical" database backups in that they extract logical definitions and data from the database to a file.
Cold or Off-line Backups - Shut the database down and backup up ALL data, log, and control files.
Hot or On-line Backups - If the databases are available and in ARCHIVELOG mode, set the tablespaces into backup mode and backup their files. Also remember to backup the control files and archived redo log files.
RMAN Backups - While the database is off-line or on-line, use the "rman" utility to backup the database.
It is advisable to use more than one of these methods to backup your database. For example, if you choose to do on-line database backups, also cover yourself by doing database exports. Also test ALL backup and recovery scenarios carefully. It is better to be save than sorry.
Regardless of your strategy, also remember to backup all required software libraries, parameter files, password files, etc. If your database is in ARCGIVELOG mode, you also need to backup archived log files.
What is the difference between online and offline backups? (for DBA)
A hot backup is a backup performed while the database is online and available for read/write. Except for Oracle exports, one can only do on-line backups when running in ARCHIVELOG mode.
A cold backup is a backup performed while the database is off-line and unavailable to its users.
What is the difference between restoring and recovering? (for DBA)
Restoring involves copying backup files from secondary storage (backup media) to disk. This can be done to replace damaged files or to copy/move a database to a new location.
Recovery is the process of applying redo logs to the database to roll it forward. One can roll-forward until a specific point-in-time (before the disaster occurred), or roll-forward until the last transaction recorded in the log files. Sql> connect SYS as SYSDBA
Sql> RECOVER DATABASE UNTIL TIME '2001-03-06:16:00:00' USING BACKUP CONTROLFILE;
How does one backup a database using the export utility? (for DBA)
Oracle exports are "logical" database backups (not physical) as they extract data and logical definitions from the database into a file. Other backup strategies normally back-up the physical data files.
One of the advantages of exports is that one can selectively re-import tables, however one cannot roll-forward from an restored export file. To completely restore a database from an export file one practically needs to recreate the entire database.
Always do full system level exports (FULL=YES). Full exports include more information about the database in the export file than user level exports.
What are the built_ins used the display the LOV?
Show_lov
List_values

How do you call other Oracle Products from Oracle Forms?
Run_product is a built-in, Used to invoke one of the supported oracle tools products and specifies the name of the document or module to be run. If the called product is unavailable at the time of the call, Oracle Forms returns a message to the operator.
What is the main diff. bet. Reports 2.0 & Reports 2.5?
Report 2.5 is object oriented.
What are the Built-ins to display the user-named editor?
A user named editor can be displayed programmatically with the built in procedure SHOW-EDITOR, EDIT_TETITEM independent of any particular text item.
How many number of columns a record group can have?
A record group can have an unlimited number of columns of type CHAR, LONG, NUMBER, or DATE provided that the total number of column does not exceed 64K.
What is a Query Record Group?
A query record group is a record group that has an associated SELECT statement. The columns in a query record group derive their default names, data types, had lengths from the database columns referenced in the SELECT statement. The records in query record group are the rows retrieved by the query associated with that record group.
What does the term panel refer to with regard to pages?
A panel is the no. of physical pages needed to print one logical page.
What is a master detail relationship?
A master detail relationship is an association between two base table blocks- a master block and a detail block. The relationship between the blocks reflects a primary key to foreign key relationship between the tables on which the blocks are based.
What is a library?
A library is a collection of subprograms including user named procedures, functions and packages.
What is an anchoring object & what is its use? What are the various sub events a mouse double click event involves?
An anchoring object is a print condition object which used to explicitly or implicitly anchor other objects to itself.
Use the add_group_column function to add a column to record group that was created at a design time?
False
What are the various sub events a mouse double click event involves? What are the various sub events a mouse double click event involves?
Double clicking the mouse consists of the mouse down, mouse up, mouse click, mouse down & mouse up events.
What is the use of break group? What are the various sub events a mouse double click event involves?
A break group is used to display one record for one group ones. While multiple related records in other group can be displayed.
What tuning indicators can one use? (for DBA)
The following high-level tuning indicators can be used to establish if a database is performing optimally or not:
. Buffer Cache Hit Ratio
Formula: Hit Ratio = (Logical Reads - Physical Reads) / Logical Reads
Action: Increase DB_CACHE_SIZE (DB_BLOCK_BUFFERS prior to 9i) to increase hit ratio
. Library Cache Hit Ratio
Action: Increase the SHARED_POOL_SIZE to increase hit ratio
What tools/utilities does Oracle provide to assist with performance tuning? (for DBA)
Oracle provide the following tools/ utilities to assist with performance monitoring and tuning:
. TKProf
. UTLBSTAT.SQL and UTLESTAT.SQL - Begin and end stats monitoring
. Statspack
. Oracle Enterprise Manager - Tuning Pack
What is STATSPACK and how does one use it? (for DBA)
Statspack is a set of performance monitoring and reporting utilities provided by Oracle from Oracle8i and above. Statspack provides improved BSTAT/ESTAT functionality, though the old BSTAT/ESTAT scripts are still available. For more information about STATSPACK, read the documentation in file $ORACLE_HOME/rdbms/admin/spdoc.txt.
Install Statspack:
cd $ORACLE_HOME/rdbms/admin
sqlplus "/ as sysdba" @spdrop.sql -- Install Statspack -
sqlplus "/ as sysdba" @spcreate.sql-- Enter tablespace names when prompted
Use Statspack:
sqlplus perfstat/perfstat
exec statspack.snap; -- Take a performance snapshots
exec statspack.snap;
o Get a list of snapshots
select SNAP_ID, SNAP_TIME from STATS$SNAPSHOT;
@spreport.sql -- Enter two snapshot id's for difference report
Other Statspack Scripts:
. sppurge.sql - Purge a range of Snapshot Id's between the specified begin and end Snap Id's
. spauto.sql - Schedule a dbms_job to automate the collection of STATPACK statistics
. spcreate.sql - Installs the STATSPACK user, tables and package on a database (Run as SYS).
. spdrop.sql - Deinstall STATSPACK from database (Run as SYS)
. sppurge.sql - Delete a range of Snapshot Id's from the database
. spreport.sql - Report on differences between values recorded in two snapshots
. sptrunc.sql - Truncates all data in Statspack tables

What are the common RMAN errors (with solutions)? (for DBA)
Some of the common RMAN errors are:
RMAN-20242: Specification does not match any archivelog in the recovery catalog.
Add to RMAN script: sql 'alter system archive log current';
RMAN-06089: archived log xyz not found or out of sync with catalog
Execute from RMAN: change archivelog all validate;
How can you execute the user defined triggers in forms 3.0 ?
Execute Trigger (trigger-name)

What ERASE package procedure does ?
Erase removes an indicated global variable.
What is the difference between NAME_IN and COPY ?
Copy is package procedure and writes values into a field.
Name in is a package function and returns the contents of the variable to which you apply.
What package procedure is used for calling another form ?
Call (E.g. Call(formname)
When the form is running in DEBUG mode, If you want to examine the values of global variables and other form variables, What package procedure command you would use in your trigger text ?
Break.
SYSTEM VARIABLES

The value recorded in system.last_record variable is of type
a. Number
b. Boolean
c. Character. ?
b. Boolean.
What is mean by Program Global Area (PGA) ?
It is area in memory that is used by a Single Oracle User Process.
What is hit ratio ?
It is a measure of well the data cache buffer is handling requests for data. Hit Ratio = (Logical Reads - Physical Reads - Hits Misses)/ Logical Reads.
How do u implement the If statement in the Select Statement
We can implement the if statement in the select statement by using the Decode statement. e.g. select DECODE (EMP_CAT,'1','First','2','Second'Null); Here the Null is the else statement where null is done .

How many types of Exceptions are there
There are 2 types of exceptions. They are
a) System Exceptions
e.g. When no_data_found, When too_many_rows
b) User Defined Exceptions
e.g. My_exception exception
When My_exception then
What are the inline and the precompiler directives
The inline and precompiler directives detect the values directly
How do you use the same lov for 2 columns
We can use the same lov for 2 columns by passing the return values in global values and using the global values in the code
How many minimum groups are required for a matrix report
The minimum number of groups in matrix report are 4
What is the difference between static and dynamic lov
The static lov contains the predetermined values while the dynamic lov contains values that come at run time
How does one manage Oracle database users? (for DBA)
Oracle user accounts can be locked, unlocked, forced to choose new passwords, etc. For example, all accounts except SYS and SYSTEM will be locked after creating an Oracle9iDB database using the DB Configuration Assistant (dbca). DBA's must unlock these accounts to make them available to users.
Look at these examples:
ALTER USER scott ACCOUNT LOCK -- lock a user account
ALTER USER scott ACCOUNT UNLOCK; -- unlocks a locked users account
ALTER USER scott PASSWORD EXPIRE; -- Force user to choose a new password
What is the difference between DBFile Sequential and Scattered Reads?(for DBA)
Both "db file sequential read" and "db file scattered read" events signify time waited for I/O read requests to complete. Time is reported in 100's of a second for Oracle 8i releases and below, and 1000's of a second for Oracle 9i and above. Most people confuse these events with each other as they think of how data is read from disk. Instead they should think of how data is read into the SGA buffer cache.
db file sequential read:
A sequential read operation reads data into contiguous memory (usually a single-block read with p3=1, but can be multiple blocks). Single block I/Os are usually the result of using indexes. This event is also used for rebuilding the control file and reading data file headers (P2=1). In general, this event is indicative of disk contention on index reads.
db file scattered read:
Similar to db file sequential reads, except that the session is reading multiple data blocks and scatters them into different discontinuous buffers in the SGA. This statistic is NORMALLY indicating disk contention on full table scans. Rarely, data from full table scans could be fitted into a contiguous buffer area, these waits would then show up as sequential reads instead of scattered reads.
The following query shows average wait time for sequential versus scattered reads:
prompt "AVERAGE WAIT TIME FOR READ REQUESTS"
select a.average_wait "SEQ READ", b.average_wait "SCAT READ"
from sys.v_$system_event a, sys.v_$system_event b
where a.event = 'db file sequential read'
and b.event = 'db file scattered read';
What is the use of PARFILE option in EXP command ?
Name of the parameter file to be passed for export.
What is the use of TABLES option in EXP command ?
List of tables should be exported.ze)

What is the OPTIMAL parameter?
It is used to set the optimal length of a rollback segment.
How does one use ORADEBUG from Server Manager/ SQL*Plus? (for DBA)
Execute the "ORADEBUG HELP" command from svrmgrl or sqlplus to obtain a list of valid ORADEBUG commands. Look at these examples:
SQLPLUS> REM Trace SQL statements with bind variables
SQLPLUS> oradebug setospid 10121
Oracle pid: 91, Unix process pid: 10121, image: oracleorcl
SQLPLUS> oradebug EVENT 10046 trace name context forever, level 12
Statement processed.
SQLPLUS> ! vi /app/oracle/admin/orcl/bdump/ora_10121.trc
SQLPLUS> REM Trace Process Statistics
SQLPLUS> oradebug setorapid 2
Unix process pid: 1436, image: ora_pmon_orcl
SQLPLUS> oradebug procstat
Statement processed.
SQLPLUS>> oradebug TRACEFILE_NAME
/app/oracle/admin/orcl/bdump/pmon_1436.trc
SQLPLUS> REM List semaphores and shared memory segments in use
SQLPLUS> oradebug ipc
SQLPLUS> REM Dump Error Stack
SQLPLUS> oradebug setospid <pid>
SQLPLUS> oradebug event immediate trace name errorstack level 3
SQLPLUS> REM Dump Parallel Server DLM locks
SQLPLUS> oradebug lkdebug -a convlock
SQLPLUS> oradebug lkdebug -a convres
SQLPLUS> oradebug lkdebug -r <resource handle> (i.e 0x8066d338 from convres dump)
Are there any undocumented commands in Oracle? (for DBA)
Sure there are, but it is hard to find them. Look at these examples:
From Server Manager (Oracle7.3 and above): ORADEBUG HELP
It looks like one can change memory locations with the ORADEBUG POKE command. Anyone brave enough to test this one for us? Previously this functionality was available with ORADBX (ls -l $ORACLE_HOME/rdbms/lib/oradbx.o; make -f oracle.mk oradbx) SQL*Plus: ALTER SESSION SET CURRENT_SCHEMA = SYS
If the maximum record retrieved property of the query is set to 10 then a summary value will be calculated?
Only for 10 records.
What are the different objects that you cannot copy or reference in object groups?
Objects of different modules
Another object groups
Individual block dependent items
Program units.
What is an OLE?
Object Linking & Embedding provides you with the capability to integrate objects from many Ms-Windows applications into a single compound document creating integrated applications enables you to use the features form .
Can a repeating frame be created without a data group as a base?
No

Is it possible to set a filter condition in a cross product group in matrix reports?
No
What is Overloading of procedures ?
The Same procedure name is repeated with parameters of different datatypes and parameters in different positions, varying number of parameters is called overloading of procedures. e.g. DBMS_OUTPUT put_line
What are the return values of functions SQLCODE and SQLERRM ? What is Pragma EXECPTION_INIT ? Explain the usage ?
SQLCODE returns the latest code of the error that has occurred.
SQLERRM returns the relevant error message of the SQLCODE.
What are the datatypes a available in PL/SQL ?
Some scalar data types such as NUMBER, VARCHAR2, DATE, CHAR, LONG, BOOLEAN. Some composite data types such as RECORD & TABLE.
What are the two parts of a procedure ?
Procedure Specification and Procedure Body.
What is the basic structure of PL/SQL ?
PL/SQL uses block structure as its basic structure. Anonymous blocks or nested blocks can be used in PL/SQL
What is PL/SQL table ?
Objects of type TABLE are called "PL/SQL tables", which are modeled as (but not the same as) database tables, PL/SQL tables use a primary PL/SQL tables can have one column and a primary key. Cursors
WHAT IS RMAN ? (for DBA)
Recovery Manager is a tool that: manages the process of creating backups and also manages the process of restoring and recovering from them.

WHY USE RMAN ? (for DBA)
No extra costs Its available free
?RMAN introduced in Oracle 8 it has become simpler with newer versions and easier than user managed backups
?Proper security
?You are 100% sure your database has been backed up.
?Its contains detail of the backups taken etc in its central repository
Facility for testing validity of backups also commands like crosscheck to check the status of backup.
Faster backups and restores compared to backups without RMAN
RMAN is the only backup tool which supports incremental backups.
Oracle 10g has got further optimized incremental backup which has resulted in improvement of performance during backup and recovery time
Parallel operations are supported
Better querying facility for knowing different details of backup
No extra redo generated when backup is taken..compared to online
backup without RMAN which results in saving of space in hard disk
RMAN an intelligent tool
Maintains repository of backup metadata
Remembers backup set location
Knows what need to backed up
Knows what is required for recovery
Knows what backups are redundant
UNDERSTANDING THE RMAN ARCHITECTURE
An oracle RMAN comprises of
RMAN EXECUTABLE This could be present and fired even through client side
TARGET DATABASE This is the database which needs to be backed up .
RECOVERY CATALOG Recovery catalog is optional otherwise backup details are stored in target database controlfile .
It is a repository of information queried and updated by Recovery Manager
It is a schema or user stored in Oracle database. One schema can support many databases
It contains information about physical schema of target database datafile and archive log ,backup sets and pieces Recovery catalog is a must in following scenarios
. In order to store scripts
. For tablespace point in time recovery

Media Management Software
Media Management software is a must if you are using RMAN for storing backup in tape drive directly.

Backups in RMAN
Oracle backups in RMAN are of the following type
RMAN complete backup OR RMAN incremental backup
These backups are of RMAN proprietary nature

IMAGE COPY
The advantage of uing Image copy is its not in RMAN proprietary format..

Backup Format
RMAN backup is not in oracle format but in RMAN format. Oracle backup comprises of backup sets and it consists of backup pieces. Backup sets are logical entity In oracle 9i it gets stored in a default location There are two type of backup sets Datafile backup sets, Archivelog backup sets One more important point of data file backup sets is it do not include empty blocks. A backup set would contain many backup pieces.
A single backup piece consists of physical files which are in RMAN proprietary format.

Example of taking backup using RMAN
Taking RMAN Backup
In non archive mode in dos prompt type
RMAN
You get the RMAN prompt
RMAN > Connect Target
Connect to target database : Magic
using target database controlfile instead of recovery catalog

Lets take a simple backup of database in non archive mode
shutdown immediate ; - - Shutdowns the database
startup mount
backup database ;- its start backing the database
alter database open;
We can fire the same command in archive log mode
And whole of datafiles will be backed
Backup database plus archivelog;

Restoring database
Restoring database has been made very simple in 9i .
It is just
Restore database..
RMAN has become intelligent to identify which datafiles has to be restored
and the location of backuped up file.

Oracle Enhancement for RMAN in 10 G

Flash Recovery Area
Right now the price of hard disk is falling. Many dba are taking oracle database backup inside the hard disk itself since it results in lesser mean time between recoverability.
The new parameter introduced is
DB_RECOVERY_FILE_DEST = /oracle/flash_recovery_area
By configuring the RMAN RETENTION POLICY the flash recovery area will automatically delete obsolete backups and archive logs that are no longer required based on that configuration Oracle has introduced new features in incremental backup

Change Tracking File
Oracle 10g has the facility to deliver faster incrementals with the implementation of changed tracking file feature.This will results in faster backups lesser space consumption and also reduces the time needed for daily backups

Incrementally Updated Backups
Oracle database 10g Incrementally Updates Backup features merges the image copy of a datafile with RMAN incremental backup. The resulting image copy is now updated with block changes captured by incremental backups.The merging of the image copy and incremental backup is initiated with RMAN recover command. This results in faster recovery.

Binary compression technique reduces backup space usage by 50-75%.

With the new DURATION option for the RMAN BACKUP command, DBAs can weigh backup performance against system service level requirements. By specifying a duration, RMAN will automatically calculate the appropriate backup rate; in addition, DBAs can optionally specify whether backups should minimize time or system load.

New Features in Oem to identify RMAN related backup like backup pieces, backup sets and image copy

Oracle 9i New features Persistent RMAN Configuration
A new configure command has been introduced in Oracle 9i , that lets you configure various features including automatic channels, parallelism ,backup options, etc.
These automatic allocations and options can be overridden by commands in a RMAN command file.

Controlfile Auto backups
Through this new feature RMAN will automatically perform a controlfile auto backup. after every backup or copy command.

Block Media Recovery
If we can restore a few blocks rather than an entire file we only need few blocks.
We even dont need to bring the data file offline.
Syntax for it as follows
Block Recover datafile 8 block 22;

Configure Backup Optimization
Prior to 9i whenever we backed up database using RMAN our backup also used take backup of read only table spaces which had already been backed up and also the same with archive log too.
Now with 9i backup optimization parameter we can prevent repeat backup of read only tablespace and archive log. The command for this is as follows Configure backup optimization on

Archive Log failover
If RMAN cannot read a block in an archived log from a destination. RMAN automatically attempts to read from an alternate location this is called as archive log failover

There are additional commands like
backup database not backed up since time '31-jan-2002 14:00:00'
Do not backup previously backed up files
(say a previous backup failed and you want to restart from where it left off).
Similar syntax is supported for restores
backup device sbt backup set all Copy a disk backup to tape
(backing up a backup
Additionally it supports
. Backup of server parameter file
. Parallel operation supported
. Extensive reporting available
. Scripting
. Duplex backup sets
. Corrupt block detection
. Backup archive logs

Pitfalls of using RMAN
Previous to version Oracle 9i backups were not that easy which means you had to allocate a channel compulsorily to take backup You had to give a run etc . The syntax was a bit complex RMAN has now become very simple and easy to use..
If you changed the location of backup set it is compulsory for you to register it using RMAN or while you are trying to restore backup It resulted in hanging situations
There is no method to know whether during recovery database restore is going to fail because of missing archive log file.
Compulsory Media Management only if using tape backup
Incremental backups though used to consume less space used to be slower since it used to read the entire database to find the changed blocks and also They have difficult time streaming the tape device. .
Considerable improvement has been made in 10g to optimize the algorithm to handle changed block.

Observation
Introduced in Oracle 8 it has become more powerful and simpler with newer version of Oracle 9 and 10 g.
So if you really don't want to miss something critical please start using RMAN.
Explain UNION,MINUS,UNION ALL, INTERSECT ?
INTERSECT returns all distinct rows selected by both queries.MINUS - returns all distinct rows selected by the first query but not by the second.UNION - returns all distinct rows selected by either queryUNION ALL - returns all rows selected by either query, including all duplicates.
Should the OEM Console be displayed at all times (when there are scheduled jobs)? (for DBA)
When a job is submitted the agent will confirm the status of the job. When the status shows up as scheduled, you can close down the OEM console. The processing of the job is managed by the OIA (Oracle Intelligent Agent). The OIA maintains a .jou file in the agent's subdirectory. When the console is launched communication with the Agent is established and the contents of the .jou file (binary) are reported to the console job subsystem. Note that OEM will not be able to send e-mail and paging notifications when the Console is not started.
Difference between SUBSTR and INSTR ?
INSTR (String1,String2(n,(m)),INSTR returns the position of the mth occurrence of the string 2 instring1. The search begins from nth position of string1.SUBSTR (String1 n,m)SUBSTR returns a character string of size m in string1, starting from nth position of string1.
What kind of jobs can one schedule with OEM? (for DBA)
OEM comes with pre-defined jobs like Export, Import, run OS commands, run sql scripts, SQL*Plus commands etc. It also gives you the flexibility of scheduling custom jobs written with the TCL language.
What are the pre requisites ?
I. to modify data type of a column ? ii. to add a column with NOT NULL constraint ? To Modify the datatype of a column the column must be empty. to add a column with NOT NULL constrain, the table must be empty.
How does one backout events and jobs during maintenance slots? (for DBA)
Managemnet and data collection activity can be suspended by imposing a blackout. Look at these examples:
agentctl start blackout # Blackout the entrire agent
agentctl stop blackout # Resume normal monitoring and management
agentctl start blackout ORCL # Blackout database ORCL
agentctl stop blackout ORCL # Resume normal monitoring and management
agentctl start blackout -s jobs -d 00:20 # Blackout jobs for 20 minutes
What are the types of SQL Statement ?
Data Definition Language :
CREATE,ALTER,DROP,TRUNCATE,REVOKE,NO AUDIT & COMMIT.

Data Manipulation Language:
INSERT,UPDATE,DELETE,LOCK

TABLE,EXPLAIN PLAN & SELECT.Transactional Control:
COMMIT & ROLLBACKSession Control: ALTERSESSION & SET

ROLESystem Control :
ALTER SYSTEM.
What is the Oracle Intelligent Agent? (for DBA)
The Oracle Intelligent Agent (OIA) is an autonomous process that needs to run on a remote node in the network to make the node OEM manageable. The Oracle Intelligent Agent is responsible for:
. Discovering targets that can be managed (Database Servers, Net8 Listeners, etc.);
. Monitoring of events registered in Enterprise Manager; and
. Executing tasks associated with jobs submitted to Enterprise Manager.
How does one start the Oracle Intelligent Agent? (for DBA)
One needs to start an OIA (Oracle Intelligent Agent) process on all machines that will to be managed via OEM.
For OEM 9i and above:
agentctl start agent
agentctl stop agent

For OEM 2.1 and below:
lsnrctl dbsnmp_start
lsnrctl dbsnmp_status

On Windows NT, start the "OracleAgent" Service.
If the agent doesn't want to start, ensure your environment variables are set correctly and delete the following files before trying again:
1) In $ORACLE_HOME/network/admin: snmp_ro.ora and snmp_rw.ora.
2) Also delete ALL files in $ORACLE_HOME/network/agent/.
Can one write scripts to send alert messages to the console?
Start the OEM console and create a new event. Select option "Enable Unsolicited Event". Select test "Unsolicited Event". When entering the parameters, enter values similar to these:
Event Name: /oracle/script/myalert
Object: *
Severity: *
Message: *
One can now write the script and invoke the oemevent command to send alerts to the console. Look at this example: oemevent /oracle/script/myalert DESTINATION alert "My custom error message" where DESTINATION is the same value as entered in the "Monitored Destinations" field when you've registered the event in the OEM Console.
Where can one get more information about TCL? (for DBA)
One can write custom event checking routines for OEM using the TCL (Tool Command Language) language. Check the following sites for more information about TCL:
. The Tcl Developer Xchange - download and learn about TCL
. OraTCL at Sourceforge - Download the OraTCL package
. Tom Poindexter's Tcl Page - Oratcl was originally written by Tom Poindexter
Are there any troubleshooting tips for OEM? (for DBA)
. Create the OEM repository with a user (which will manage the OEM) and store it in a tablespace that does not share any data with other database users. It is a bad practice to create the repository with SYS and System.
. If you are unable to launch the console or there is a communication problem with the intelligent agent (daemon). Ensure OCX files are registered. Type the following in the DOS prompt (the current directory should be $ORACLE_HOME\BIN:
C:\Orawin95\Bin> RegSvr32 mmdx32.OCX
C:\Orawin95\Bin> RegSvr32 vojt.OCX
. If you have a problem starting the Oracle Agent
Solution A: Backup the *.Q files and Delete all the *.Q Files ($Oracle_home/network/agent folder)
Backup and delete SNMP_RO.ora, SNMP_RW.ora, dbsnmp.ver and services.ora files ($Oracle_Home/network/admin folder) Start the Oracle Agent service.
Solution B: Your version of Intelligent Agent could be buggy. Check with Oracle for any available patches. For example, the Intelligent Agent that comes with Oracle 8.0.4 is buggy.
Sometimes you get a Failed status for the job that was executed successfully.
Check the log to see the results of the execution rather than relying on this status.
What is import/export and why does one need it? (for DBA)
The Oracle export (EXP) and import (IMP) utilities are used to perform logical database backup and recovery. They are also used to move Oracle data from one machine, database or schema to another.
The imp/exp utilities use an Oracle proprietary binary file format and can thus only be used between Oracle databases. One cannot export data and expect to import it into a non-Oracle database. For more information on how to load and unload data from files, read the SQL*Loader FAQ.
The export/import utilities are also commonly used to perform the following tasks:
. Backup and recovery (small databases only)
. Reorganization of data/ Eliminate database fragmentation
. Detect database corruption. Ensure that all the data can be read.
. Transporting tablespaces between databases
. Etc.

What is a display item?
Display items are similar to text items but store only fetched or assigned values. Operators cannot navigate to a display item or edit the value it contains.
How does one use the import/export utilities? (for DBA)
Look for the "imp" and "exp" executables in your $ORACLE_HOME/bin directory. One can run them interactively, using command line parameters, or using parameter files. Look at the imp/exp parameters before starting. These parameters can be listed by executing the following commands: "exp help=yes" or "imp help=yes".
The following examples demonstrate how the imp/exp utilities can be used:
exp scott/tiger file=emp.dmp log=emp.log tables=emp rows=yes indexes=no
exp scott/tiger file=emp.dmp tables=(emp,dept)
imp scott/tiger file=emp.dmp full=yes
imp scott/tiger file=emp.dmp fromuser=scott touser=scott tables=dept
exp userid=scott/tiger@orcl parfile=export.txt
... where export.txt contains:
BUFFER=100000
FILE=account.dmp
FULL=n
OWNER=scott
GRANTS=y
COMPRESS=y
NOTE: If you do not like command line utilities, you can import and export data with the "Schema Manager" GUI that ships with Oracle Enterprise Manager (OEM).
What are the types of visual attribute settings?
Custom Visual attributes Default visual attributes Named Visual attributes. Window

Can one export a subset of a table? (for DBA)
From Oracle8i one can use the QUERY= export parameter to selectively unload a subset of the data from a table. Look at this example:
exp scott/tiger tables=emp query=\"where deptno=10\"
What are the two ways to incorporate images into a oracle forms application?
Boilerplate Images
Image_items

Can one monitor how fast a table is imported? (for DBA)
If you need to monitor how fast rows are imported from a running import job, try one of the following methods:
Method 1:
select substr(sql_text,instr(sql_text,'INTO "'),30) table_name,
rows_processed,
round((sysdate-to_date(first_load_time,'yyyy-mm-dd hh24:mi:ss'))*24*60,1) minutes,
trunc(rows_processed/((sysdate-to_date(first_load_time,'yyyy-mm-dd hh24:mi:ss'))*24*60)) rows_per_min
from sys.v_$sqlarea
where sql_text like 'INSERT %INTO "%'
and command_type = 2
and open_versions > 0;
For this to work one needs to be on Oracle 7.3 or higher (7.2 might also be OK). If the import has more than one table, this statement will only show information about the current table being imported.
Contributed by Osvaldo Ancarola, Bs. As. Argentina.
Method 2:
Use the FEEDBACK=n import parameter. This command will tell IMP to display a dot for every N rows imported.
Can one import tables to a different tablespace? (for DBA)
Oracle offers no parameter to specify a different tablespace to import data into. Objects will be re-created in the tablespace they were originally exported from. One can alter this behaviour by following one of these procedures: Pre-create the table(s) in the correct tablespace:
. Import the dump file using the INDEXFILE= option
. Edit the indexfile. Remove remarks and specify the correct tablespaces.
. Run this indexfile against your database, this will create the required tables in the appropriate tablespaces
. Import the table(s) with the IGNORE=Y option.
Change the default tablespace for the user:

. Revoke the "UNLIMITED TABLESPACE" privilege from the user
. Revoke the user's quota from the tablespace from where the object was exported. This forces the import utility to create tables in the user's default tablespace.
. Make the tablespace to which you want to import the default tablespace for the user
. Import the table
What do you mean by a block in forms4.0?
Block is a single mechanism for grouping related items into a functional unit for storing, displaying and manipulating records.
How is possible to restrict the user to a list of values while entering values for parameters?
By setting the Restrict To List property to true in the parameter property sheet.
What is SQL*Loader and what is it used for? (for DBA)
SQL*Loader is a bulk loader utility used for moving data from external files into the Oracle database. Its syntax is similar to that of the DB2 Load utility, but comes with more options. SQL*Loader supports various load formats, selective loading, and multi-table loads.
How does one use the SQL*Loader utility? (for DBA)
One can load data into an Oracle database by using the sqlldr (sqlload on some platforms) utility. Invoke the utility without arguments to get a list of available parameters. Look at the following example:
sqlldr scott/tiger control=loader.ctl
This sample control file (loader.ctl) will load an external data file containing delimited data:
load data
infile 'c:\data\mydata.csv'
into table emp
fields terminated by "," optionally enclosed by '"'
( empno, empname, sal, deptno )
The mydata.csv file may look like this:
10001,"Scott Tiger", 1000, 40
10002,"Frank Naude", 500, 20
Another Sample control file with in-line data formatted as fix length records. The trick is to specify "*" as the name of the data file, and use BEGINDATA to start the data section in the control file.
load data
infile *
replace
into table departments
( dept position (02:05) char(4),
deptname position (08:27) char(20)
)
begindata
COSC COMPUTER SCIENCE
ENGL ENGLISH LITERATURE
MATH MATHEMATICS
POLY POLITICAL SCIENCE
How can a cross product be created?
By selecting the cross products tool and drawing a new group surrounding the base group of the cross products.

Is there a SQL*Unloader to download data to a flat file? (for DBA)
Oracle does not supply any data unload utilities. However, you can use SQL*Plus to select and format your data and then spool it to a file:
set echo off newpage 0 space 0 pagesize 0 feed off head off trimspool on
spool oradata.txt
select col1 || ',' || col2 || ',' || col3
from tab1
where col2 = 'XYZ';
spool off
Alternatively use the UTL_FILE PL/SQL package:
rem Remember to update initSID.ora, utl_file_dir='c:\oradata' parameter
declare
fp utl_file.file_type;
begin
fp := utl_file.fopen('c:\oradata','tab1.txt','w');
utl_file.putf(fp, '%s, %s\n', 'TextField', 55);
utl_file.fclose(fp);
end;
/
You might also want to investigate third party tools like SQLWays from Ispirer Systems, TOAD from Quest, or ManageIT Fast Unloader from CA to help you unload data from Oracle.

Can one load variable and fix length data records? (for DBA)
Yes, look at the following control file examples. In the first we will load delimited data (variable length):
LOAD DATA
INFILE *
INTO TABLE load_delimited_data
FIELDS TERMINATED BY "," OPTIONALLY ENCLOSED BY '"'
TRAILING NULLCOLS
( data1,
data2
)
BEGINDATA
11111,AAAAAAAAAA
22222,"A,B,C,D,"
If you need to load positional data (fixed length), look at the following control file example:
LOAD DATA
INFILE *
INTO TABLE load_positional_data
( data1 POSITION(1:5),
data2 POSITION(6:15)
)
BEGINDATA
11111AAAAAAAAAA
22222BBBBBBBBBB
Can one skip header records load while loading?
Use the "SKIP n" keyword, where n = number of logical rows to skip. Look at this example:
LOAD DATA
INFILE *
INTO TABLE load_positional_data
SKIP 5
( data1 POSITION(1:5),
data2 POSITION(6:15)
)
BEGINDATA
11111AAAAAAAAAA
22222BBBBBBBBBB
Can one modify data as it loads into the database? (for DBA)
Data can be modified as it loads into the Oracle Database. Note that this only applies for the conventional load path and not for direct path loads.
LOAD DATA
INFILE *
INTO TABLE modified_data
( rec_no "my_db_sequence.nextval",
region CONSTANT '31',
time_loaded "to_char(SYSDATE, 'HH24:MI')",
data1 POSITION(1:5) ":data1/100",
data2 POSITION(6:15) "upper(:data2)",
data3 POSITION(16:22)"to_date(:data3, 'YYMMDD')"
)
BEGINDATA
11111AAAAAAAAAA991201
22222BBBBBBBBBB990112
LOAD DATA
INFILE 'mail_orders.txt'
BADFILE 'bad_orders.txt'
APPEND
INTO TABLE mailing_list
FIELDS TERMINATED BY ","
( addr,
city,
state,
zipcode,
mailing_addr "decode(:mailing_addr, null, :addr, :mailing_addr)",
mailing_city "decode(:mailing_city, null, :city, :mailing_city)",
mailing_state
)

Can one load data into multiple tables at once? (for DBA)
Look at the following control file:
LOAD DATA
INFILE *
REPLACE
INTO TABLE emp
WHEN empno != ' '
( empno POSITION(1:4) INTEGER EXTERNAL,
ename POSITION(6:15) CHAR,
deptno POSITION(17:18) CHAR,
mgr POSITION(20:23) INTEGER EXTERNAL
)
INTO TABLE proj
WHEN projno != ' '
( projno POSITION(25:27) INTEGER EXTERNAL,
empno POSITION(1:4) INTEGER EXTERNAL
)

What is the difference between boiler plat images and image items?
Boiler plate Images are static images (Either vector or bit map) that you import from the file system or database to use a graphical elements in your form, such as company logos and maps. Image items are special types of interface controls that store and display either vector or bitmap images. Like other items that store values, image items can be either base table items(items that relate directly to database columns) or control items. The definition of an image item is stored as part of the form module FMB and FMX files, but no image file is actually associated with an image item until the item is populate at run time.
What are the triggers available in the reports?
Before report, Before form, After form , Between page, After report.
Why is a Where clause faster than a group filter or a format trigger?
Because, in a where clause the condition is applied during data retrievalthan after retrieving the data.
Can one selectively load only the records that one need? (for DBA)
Look at this example, (01) is the first character, (30:37) are characters 30 to 37:
LOAD DATA
INFILE 'mydata.dat' BADFILE 'mydata.bad' DISCARDFILE 'mydata.dis'
APPEND
INTO TABLE my_selective_table
WHEN (01) <> 'H' and (01) <> 'T' and (30:37) = '19991217'
(
region CONSTANT '31',
service_key POSITION(01:11) INTEGER EXTERNAL,
call_b_no POSITION(12:29) CHAR
)
Can one skip certain columns while loading data? (for DBA)
One cannot use POSTION(x:y) with delimited data. Luckily, from Oracle 8i one can specify FILLER columns. FILLER columns are used to skip columns/fields in the load file, ignoring fields that one does not want. Look at this example: -- One cannot use POSTION(x:y) as it is stream data, there are no positional fields-the next field begins after some delimiter, not in column X. -->
LOAD DATA
TRUNCATE INTO TABLE T1
FIELDS TERMINATED BY ','
( field1,
field2 FILLER,
field3
)
How does one load multi-line records? (for DBA)
One can create one logical record from multiple physical records using one of the following two clauses:
. CONCATENATE: - use when SQL*Loader should combine the same number of physical records together to form one logical record.
. CONTINUEIF - use if a condition indicates that multiple records should be treated as one. Eg. by having a '#' character in column 1.
How can get SQL*Loader to COMMIT only at the end of the load file? (for DBA)
One cannot, but by setting the ROWS= parameter to a large value, committing can be reduced. Make sure you have big rollback segments ready when you use a high value for ROWS=.
Can one improve the performance of SQL*Loader? (for DBA)
A very simple but easily overlooked hint is not to have any indexes and/or constraints (primary key) on your load tables during the load process. This will significantly slow down load times even with ROWS= set to a high value.
Add the following option in the command line: DIRECT=TRUE. This will effectively bypass most of the RDBMS processing. However, there are cases when you can't use direct load. Refer to chapter 8 on Oracle server Utilities manual.
Turn off database logging by specifying the UNRECOVERABLE option. This option can only be used with direct data loads. Run multiple load jobs concurrently.
How does one use SQL*Loader to load images, sound clips and documents? (for DBA)
SQL*Loader can load data from a "primary data file", SDF (Secondary Data file - for loading nested tables and VARRAYs) or LOGFILE. The LOBFILE method provides and easy way to load documents, images and audio clips into BLOB and CLOB columns. Look at this example:
Given the following table:
CREATE TABLE image_table (
image_id NUMBER(5),
file_name VARCHAR2(30),
image_data BLOB);
Control File:
LOAD DATA
INFILE *
INTO TABLE image_table
REPLACE
FIELDS TERMINATED BY ','
(
image_id INTEGER(5),
file_name CHAR(30),
image_data LOBFILE (file_name) TERMINATED BY EOF
)
BEGINDATA
001,image1.gif
002,image2.jpg
What is the difference between the conventional and direct path loader? (for DBA)
The conventional path loader essentially loads the data by using standard INSERT statements. The direct path loader (DIRECT=TRUE) bypasses much of the logic involved with that, and loads directly into the Oracle data files. More information about the restrictions of direct path loading can be obtained from the Utilities Users Guide.
GENERAL INTERVIEW QUESTIONS
What are the various types of Exceptions ?
User defined and Predefined Exceptions.
Can we define exceptions twice in same block ?
No.
What is the difference between a procedure and a function ?
Functions return a single variable by value whereas procedures do not return any variable by value. Rather they return multiple variables by passing variables by reference through their OUT parameter.
Can you have two functions with the same name in a PL/SQL block ?
Yes.
Can you have two stored functions with the same name ?
Yes.
Can you call a stored function in the constraint of a table ?
No.

What are the various types of parameter modes in a procedure ?
IN, OUT AND INOUT.
What is Over Loading and what are its restrictions ?
OverLoading means an object performing different functions depending upon the no. of parameters or the data type of the parameters passed to it.
Can functions be overloaded ?
Yes.
Can 2 functions have same name & input parameters but differ only by return datatype ?
No.
What are the constructs of a procedure, function or a package ?
The constructs of a procedure, function or a package are :
variables and constants
cursors
exceptions

Why Create or Replace and not Drop and recreate procedures ?
So that Grants are not dropped.
Can you pass parameters in packages ? How ?
Yes. You can pass parameters to procedures or functions in a package.
What are the parts of a database trigger ?
The parts of a trigger are:
A triggering event or statement
A trigger restriction
A trigger action
What are the various types of database triggers ?
There are 12 types of triggers, they are combination of :
Insert, Delete and Update Triggers.
Before and After Triggers.
Row and Statement Triggers.
(3*2*2=12)
What is the advantage of a stored procedure over a database trigger ?
We have control over the firing of a stored procedure but we have no control over the firing of a trigger.
What is the maximum no. of statements that can be specified in a trigger statement ?
One.
Can views be specified in a trigger statement ?
No
What are the values of :new and :old in Insert/Delete/Update Triggers ?
INSERT : new = new value, old = NULL
DELETE : new = NULL, old = old value
UPDATE : new = new value, old = old value
What are cascading triggers? What is the maximum no of cascading triggers at a time?
When a statement in a trigger body causes another trigger to be fired, the triggers are said to be cascading. Max = 32.
What are mutating triggers ?
A trigger giving a SELECT on the table on which the trigger is written.
What are constraining triggers ?
A trigger giving an Insert/Update on a table having referential integrity constraint on the triggering table.
Describe Oracle database's physical and logical structure ?
Physical : Data files, Redo Log files, Control file.
Logical : Tables, Views, Tablespaces, etc.
Can you increase the size of a tablespace ? How ?
Yes, by adding datafiles to it.
What is the use of Control files ?
Contains pointers to locations of various data files, redo log files, etc.
What is the use of Data Dictionary ?
Used by Oracle to store information about various physical and logical Oracle structures e.g. Tables, Tablespaces, datafiles, etc
What are the advantages of clusters ?
Access time reduced for joins.
What are the disadvantages of clusters ?
The time for Insert increases.
Can Long/Long RAW be clustered ?
No.
Can null keys be entered in cluster index, normal index ?
Yes.
Can Check constraint be used for self referential integrity ? How ?
Yes. In the CHECK condition for a column of a table, we can reference some other column of the same table and thus enforce self referential integrity.
What are the min. extents allocated to a rollback extent ?
Two
What are the states of a rollback segment ? What is the difference between partly available and needs recovery ?
The various states of a rollback segment are :
ONLINE, OFFLINE, PARTLY AVAILABLE, NEEDS RECOVERY and INVALID.
What is the difference between unique key and primary key ?
Unique key can be null; Primary key cannot be null.
An insert statement followed by a create table statement followed by rollback ? Will the rows be inserted ?
No.

an you define multiple savepoints ?
Yes.
Can you Rollback to any savepoint ?
Yes.
What is the maximum no. of columns a table can have ?
254.
What is the significance of the & and && operators in PL SQL ?
The & operator means that the PL SQL block requires user input for a variable. The && operator means that the value of this variable should be the same as inputted by the user previously for this same variable. If a transaction is very large, and the rollback segment is not able to hold the rollback information, then will the transaction span across different rollback segments or will it terminate ? It will terminate (Please check ).
Can you pass a parameter to a cursor ?
Explicit cursors can take parameters, as the example below shows. A cursor parameter can appear in a query wherever a constant can appear. CURSOR c1 (median IN NUMBER) IS SELECT job, ename FROM emp WHERE sal > median;

What are the various types of RollBack Segments ?
Public Available to all instances
Private Available to specific instance
Can you use %RowCount as a parameter to a cursor ?
Yes

Is the query below allowed :
Select sal, ename Into x From emp Where ename = 'KING'
(Where x is a record of Number(4) and Char(15))
Yes
Is the assignment given below allowed :
ABC = PQR (Where ABC and PQR are records)
Yes

Is this for loop allowed :
For x in &Start..&End Loop
Yes

How many rows will the following SQL return :
Select * from emp Where rownum < 10;
9 rows
How many rows will the following SQL return :
Select * from emp Where rownum = 10;
No rows
Which symbol preceeds the path to the table in the remote database ?
@
Are views automatically updated when base tables are updated ?
Yes
Can a trigger written for a view ?
No
If all the values from a cursor have been fetched and another fetch is issued, the output will be : error, last record or first record ?
Last Record
A table has the following data : [[5, Null, 10]]. What will the average function return ?
7.5
Is Sysdate a system variable or a system function?
System Function
Consider a sequence whose currval is 1 and gets incremented by 1 by using the nextval reference we get the next number 2. Suppose at this point we issue an rollback and again issue a nextval. What will the output be ?
3
Definition of relational DataBase by Dr. Codd (IBM)?
A Relational Database is a database where all data visible to the user is organized strictly as tables of data values and where all database operations work on these tables.
What is Multi Threaded Server (MTA) ?
In a Single Threaded Architecture (or a dedicated server configuration) the database manager creates a separate process for each database user. But in MTA the database manager can assign multiple users (multiple user processes) to a single dispatcher (server process), a controlling process that queues request for work thus reducing the databases memory requirement and resources.
Which are initial RDBMS, Hierarchical & N/w database ?
RDBMS - R system
Hierarchical - IMS
N/W - DBTG
What is Functional Dependency
Given a relation R, attribute Y of R is functionally dependent on attribute X of R if and only if each X-value has associated with it precisely one -Y value in R
What is Auditing ?
The database has the ability to audit all actions that take place within it.
a) Login attempts, b) Object Accesss, c) Database Action Result of Greatest(1,NULL) or Least(1,NULL) NULL
While designing in client/server what are the 2 imp. things to be considered ?
Network Overhead (traffic), Speed and Load of client server
When to create indexes ?
To be created when table is queried for less than 2% or 4% to 25% of the table rows.

How can you avoid indexes ?
TO make index access path unavailable - Use FULL hint to optimizer for full table scan - Use INDEX or AND-EQUAL hint to optimizer to use one index or set to indexes instead of another. - Use an expression in the Where Clause of the SQL.
What is the result of the following SQL :
Select 1 from dual
UNION
Select 'A' from dual;
Error
Can database trigger written on synonym of a table and if it can be then what would be the effect if original table is accessed.
Yes, database trigger would fire.

Can you alter synonym of view or view ?
No
Can you create index on view ?
No
What is the difference between a view and a synonym ?
Synonym is just a second name of table used for multiple link of database. View can be created with many tables, and with virtual columns and with conditions. But synonym can be on view.
What is the difference between alias and synonym ?
Alias is temporary and used with one query. Synonym is permanent and not used as alias.
What is the effect of synonym and table name used in same Select statement ?
Valid
What's the length of SQL integer ?
32 bit length
What is the difference between foreign key and reference key ?
Foreign key is the key i.e. attribute which refers to another table primary key. Reference key is the primary key of table referred by another table.
Can dual table be deleted, dropped or altered or updated or inserted ?
Yes
If content of dual is updated to some value computation takes place or not ?
Yes
If any other table same as dual is created would it act similar to dual?
Yes
For which relational operators in where clause, index is not used ?
<> , like '% ...' is NOT functions, field +constant, field || ''
Assume that there are multiple databases running on one machine. How can you switch from one to another ?
Changing the ORACLE_SID
What are the advantages of Oracle ?
Portability : Oracle is ported to more platforms than any of its competitors, running on more than 100 hardware platforms and 20 networking protocols.
Market Presence : Oracle is by far the largest RDBMS vendor and spends more on R & D than most of its competitors earn in total revenue. This market clout means that you are unlikely to be left in the lurch by Oracle and there are always lots of third party interfaces available.
Backup and Recovery : Oracle provides industrial strength support for on-line backup and recovery and good software fault tolerence to disk failure. You can also do point-in-time recovery.
Performance : Speed of a 'tuned' Oracle Database and application is quite good, even with large databases. Oracle can manage > 100GB databases.
Multiple database support : Oracle has a superior ability to manage multiple databases within the same transaction using a two-phase commit protocol.
What is a forward declaration ? What is its use ?
PL/SQL requires that you declare an identifier before using it. Therefore, you must declare a subprogram before calling it. This declaration at the start of a subprogram is called forward declaration. A forward declaration consists of a subprogram specification terminated by a semicolon.
What are actual and formal parameters ?
Actual Parameters : Subprograms pass information using parameters. The variables or expressions referenced in the parameter list of a subprogram call are actual parameters. For example, the following procedure call lists two actual parameters named emp_num and amount:
Eg. raise_salary(emp_num, amount);
Formal Parameters : The variables declared in a subprogram specification and referenced in the subprogram body are formal parameters. For example, the following procedure declares two formal parameters named emp_id and increase: Eg. PROCEDURE raise_salary (emp_id INTEGER, increase REAL) IS current_salary REAL;
What are the types of Notation ?
Position, Named, Mixed and Restrictions.
What all important parameters of the init.ora are supposed to be increased if you want to increase the SGA size ?
In our case, db_block_buffers was changed from 60 to 1000 (std values are 60, 550 & 3500) shared_pool_size was changed from 3.5MB to 9MB (std values are 3.5, 5 & 9MB) open_cursors was changed from 200 to 300 (std values are 200 & 300) db_block_size was changed from 2048 (2K) to 4096 (4K) {at the time of database creation}.
The initial SGA was around 4MB when the server RAM was 32MB and The new SGA was around 13MB when the server RAM was increased to 128MB.
If I have an execute privilege on a procedure in another users schema, can I execute his procedure even though I do not have privileges on the tables within the procedure ?
Yes
What are various types of joins ?
Equijoins, Non-equijoins, self join, outer join
What is a package cursor ?
A package cursor is a cursor which you declare in the package specification without an SQL statement. The SQL statement for the cursor is attached dynamically at runtime from calling procedures.
If you insert a row in a table, then create another table and then say Rollback. In this case will the row be inserted ?
Yes. Because Create table is a DDL which commits automatically as soon as it is executed. The DDL commits the transaction even if the create statement fails internally (eg table already exists error) and not syntactically.
What are the various types of queries ??
Normal Queries
Sub Queries
Co-related queries
Nested queries
Compound queries
What is a transaction ?
A transaction is a set of SQL statements between any two COMMIT and ROLLBACK statements.
What is implicit cursor and how is it used by Oracle ?
An implicit cursor is a cursor which is internally created by Oracle. It is created by Oracle for each individual SQL.
Which of the following is not a schema object : Indexes, tables, public synonyms, triggers and packages ?
Public synonyms
What is PL/SQL?
PL/SQL is Oracle's Procedural Language extension to SQL. The language includes object oriented programming techniques such as encapsulation, function overloading, information hiding (all but inheritance), and so, brings state-of-the-art programming to the Oracle database server and a variety of Oracle tools.
Is there a PL/SQL Engine in SQL*Plus?
No. Unlike Oracle Forms, SQL*Plus does not have a PL/SQL engine. Thus, all your PL/SQL are send directly to the database engine for execution. This makes it much more efficient as SQL statements are not stripped off and send to the database individually.
Is there a limit on the size of a PL/SQL block?
Currently, the maximum parsed/compiled size of a PL/SQL block is 64K and the maximum code size is 100K. You can run the following select statement to query the size of an existing package or procedure.
SQL> select * from dba_object_size where name = 'procedure_name'
Can one read/write files from PL/SQL?
Included in Oracle 7.3 is a UTL_FILE package that can read and write files. The directory you intend writing to has to be in your INIT.ORA file (see UTL_FILE_DIR=... parameter). Before Oracle 7.3 the only means of writing a file was to use DBMS_OUTPUT with the SQL*Plus SPOOL command.
DECLARE
fileHandler UTL_FILE.FILE_TYPE;
BEGIN
fileHandler := UTL_FILE.FOPEN('/home/oracle/tmp', 'myoutput','W');
UTL_FILE.PUTF(fileHandler, 'Value of func1 is %sn', func1(1));
UTL_FILE.FCLOSE(fileHandler);
END;

How can I protect my PL/SQL source code?
PL/SQL V2.2, available with Oracle7.2, implements a binary wrapper for PL/SQL programs to protect the source code. This is done via a standalone utility that transforms the PL/SQL source code into portable binary object code (somewhat larger than the original). This way you can distribute software without having to worry about exposing your proprietary algorithms and methods. SQL*Plus and SQL*DBA will still understand and know how to execute such scripts. Just be careful, there is no "decode" command available.
The syntax is:
wrap iname=myscript.sql oname=xxxx.yyy
Can one use dynamic SQL within PL/SQL? OR Can you use a DDL in a procedure ? How ?
From PL/SQL V2.1 one can use the DBMS_SQL package to execute dynamic SQL statements.
Eg: CREATE OR REPLACE PROCEDURE DYNSQL
AS
cur integer;
rc integer;
BEGIN
cur := DBMS_SQL.OPEN_CURSOR;
DBMS_SQL.PARSE(cur,'CREATE TABLE X (Y DATE)', DBMS_SQL.NATIVE);
rc := DBMS_SQL.EXECUTE(cur);
DBMS_SQL.CLOSE_CURSOR(cur);
END;
SQL SERVER INTERVIEW QUESTIONS </>
Well a relational database is basically composed of tables that contain related data. So the Process of organizing this data into tables is actually referred to as normalization.

What is a Stored Procedure?

Its nothing but a set of T-SQL statements combined to perform a single task of several tasks. Its basically like a Macro so when you invoke the Stored procedure, you actually run a set of statements.

Can you give an example of Stored Procedure?

sp_helpdb , sp_who2, sp_renamedb are a set of system defined stored procedures. We can also have user defined stored procedures which can be called in similar way.

What is a trigger?

Triggers are basically used to implement business rules. Triggers is also similar to stored procedures. The difference is that it can be activated when data is added or edited or deleted from a table in a database.

What is a view?

If we have several tables in a db and we want to view only specific columns from specific tables we can go for views. It would also suffice the needs of security some times allowing specfic users to see only specific columns based on the permission that we can configure on the view. Views also reduce the effort that is required for writing queries to access specific columns every time.

What is an Index?

When queries are run against a db, an index on that db basically helps in the way the data is sorted to process the query for faster and data retrievals are much faster when we have an index.

What are the types of indexes available with SQL Server?

There are basically two types of indexes that we use with the SQL Server. Clustered and the Non-Clustered.

What is the basic difference between clustered and a non-clustered index?

The difference is that, Clustered index is unique for any given table and we can have only one clustered index on a table. The leaf level of a clustered index is the actual data and the data is resorted in case of clustered index. Whereas in case of non-clustered index the leaf level is actually a pointer to the data in rows so we can have as many non-clustered indexes as we can on the db.
What are cursors?

Well cursors help us to do an operation on a set of data that we retreive by commands such as Select columns from table. For example : If we have duplicate records in a table we can remove it by declaring a cursor which would check the records during retreival one by one and remove rows which have duplicate values.

When do we use the UPDATE_STATISTICS command?

This command is basically used when we do a large processing of data. If we do a large amount of deletions any modification or Bulk Copy into the tables, we need to basically update the indexes to take these changes into account. UPDATE_STATISTICS updates the indexes on these tables accordingly.

Which TCP/IP port does SQL Server run on?

SQL Server runs on port 1433 but we can also change it for better security.

From where can you change the default port?

From the Network Utility TCP/IP properties ?> Port number.both on client and the server.

Can you tell me the difference between DELETE & TRUNCATE commands?

Delete command removes the rows from a table based on the condition that we provide with a WHERE clause. Truncate will actually remove all the rows from a table and there will be no data in the table after we run the truncate command.

Can we use Truncate command on a table which is referenced by FOREIGN KEY?

No. We cannot use Truncate command on a table with Foreign Key because of referential integrity.

What is the use of DBCC commands?

DBCC stands for database consistency checker. We use these commands to check the consistency of the databases, i.e., maintenance, validation task and status checks.

Can you give me some DBCC command options?(Database consistency check)

DBCC CHECKDB - Ensures that tables in the db and the indexes are correctly linked.and DBCC CHECKALLOC - To check that all pages in a db are correctly allocated. DBCC SQLPERF - It gives report on current usage of transaction log in percentage. DBCC CHECKFILEGROUP - Checks all tables file group for any damage.

What command do we use to rename a db?

sp_renamedb ?oldname? , ?newname?

Well sometimes sp_reanmedb may not work you know because if some one is using the db it will not accept this command so what do you think you can do in such cases?

In such cases we can first bring to db to single user using sp_dboptions and then we can rename that db and then we can rerun the sp_dboptions command to remove the single user mode.

What is the difference between a HAVING CLAUSE and a WHERE CLAUSE?

Having Clause is basically used only with the GROUP BY function in a query. WHERE Clause is applied to each row before they are part of the GROUP BY function in a query.

What do you mean by COLLATION?

Collation is basically the sort order. There are three types of sort order Dictionary case sensitive, Dictonary - case insensitive and Binary.

What is a Join in SQL Server?

Join actually puts data from two or more tables into a single result set.

Can you explain the types of Joins that we can have with Sql Server?

There are three types of joins: Inner Join, Outer Join, Cross Join

When do you use SQL Profiler?

SQL Profiler utility allows us to basically track connections to the SQL Server and also determine activities such as which SQL Scripts are running, failed jobs etc..

What is a Linked Server?

Linked Servers is a concept in SQL Server by which we can add other SQL Server to a Group and query both the SQL Server dbs using T-SQL Statements.

Can you link only other SQL Servers or any database servers such as Oracle?

We can link any server provided we have the OLE-DB provider from Microsoft to allow a link. For Oracle we have a OLE-DB provider for oracle that microsoft provides to add it as a linked server to the sql server group.

Which stored procedure will you be running to add a linked server?

sp_addlinkedserver, sp_addlinkedsrvlogin

What are the OS services that the SQL Server installation adds?

MS SQL SERVER SERVICE, SQL AGENT SERVICE, DTC (Distribution transac co-ordinator)

Can you explain the role of each service?

SQL SERVER - is for running the databases SQL AGENT - is for automation such as Jobs, DB Maintanance, Backups DTC - Is for linking and connecting to other SQL Servers
How do you troubleshoot SQL Server if its running very slow?

First check the processor and memory usage to see that processor is not above 80% utilization and memory not above 40-45% utilization then check the disk utilization using Performance Monitor, Secondly, use SQL Profiler to check for the users and current SQL activities and jobs running which might be a problem. Third would be to run UPDATE_STATISTICS command to update the indexes

Lets say due to N/W or Security issues client is not able to connect to server or vice versa. How do you troubleshoot?

First I will look to ensure that port settings are proper on server and client Network utility for connections. ODBC is properly configured at client end for connection ??Makepipe & readpipe are utilities to check for connection. Makepipe is run on Server and readpipe on client to check for any connection issues.

What are the authentication modes in SQL Server?

Windows mode and mixed mode (SQL & Windows).

Where do you think the users names and passwords will be stored in sql server?

They get stored in master db in the sysxlogins table.

What is log shipping? Can we do logshipping with SQL Server

Logshipping is a new feature of SQL Server 2000. We should have two SQL Server - Enterprise Editions. From Enterprise Manager we can configure the logshipping. In logshipping the transactional log file from one server is automatically updated into the backup database on the other server. If one server fails, the other server will have the same db and we can use this as the DR (disaster recovery) plan.

Let us say the SQL Server crashed and you are rebuilding the databases including the master database what procedure to you follow?

For restoring the master db we have to stop the SQL Server first and then from command line we can type SQLSERVER .m which will basically bring it into the maintenance mode after which we can restore the master db.

Let us say master db itself has no backup. Now you have to rebuild the db so what kind of action do you take?

(I am not sure- but I think we have a command to do it).

What is BCP? When do we use it?

BulkCopy is a tool used to copy huge amount of data from tables and views. But it won?t copy the structures of the same.

What should we do to copy the tables, schema and views from one SQL Server to another?

We have to write some DTS packages for it.
What?s the difference between a primary key and a unique key?

Both primary key and unique enforce uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where are unique creates a nonclustered index by default. Another major difference is that, primary key doesn?t allow NULLs, but unique key allows one NULL only.

Write a SQL Query to find first Week Day of month?

SELECT DATENAME(dw, DATEADD(dd, - DATEPART(dd, GETDATE()) + 1, GETDATE())) AS FirstDay

How to find 6th highest salary from Employee table

SELECT TOP 1 salary FROM (SELECT DISTINCT TOP 6 salary FROM employee ORDER BY salary DESC) a ORDER BY salary

What is a join and List different types of joins.

Joins are used in queries to explain how different tables are related. Joins also let you select data from a table depending upon data from another table. Types of joins: INNER JOINs, OUTER JOINs, CROSS JOINs. OUTER JOINs are further classified as LEFT OUTER JOINS, RIGHT OUTER JOINS and FULL OUTER JOINS.

How can I enforce to use particular index?

You can use index hint (index=index_name) after the table name. SELECT au_lname FROM authors (index=aunmind)

What is sorting and what is the difference between sorting and clustered indexes?

The ORDER BY clause sorts query results by one or more columns up to 8,060 bytes. This will happen by the time when we retrieve data from database. Clustered indexes physically sorting data, while inserting/updating the table.

What are the differences between UNION and JOINS?

A join selects columns from 2 or more tables. A union selects rows.

What is the Referential Integrity?

Referential integrity refers to the consistency that must be maintained between primary and foreign keys, i.e. every foreign key value must have a corresponding primary key value
What?s the difference between a primary key and a unique key?

Both primary key and unique enforce uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where are unique creates a nonclustered index by default. Another major difference is that, primary key doesn?t allow NULLs, but unique key allows one NULL only.

Write a SQL Query to find first Week Day of month?

SELECT DATENAME(dw, DATEADD(dd, - DATEPART(dd, GETDATE()) + 1, GETDATE())) AS FirstDay

How to find 6th highest salary from Employee table

SELECT TOP 1 salary FROM (SELECT DISTINCT TOP 6 salary FROM employee ORDER BY salary DESC) a ORDER BY salary

What is a join and List different types of joins.

Joins are used in queries to explain how different tables are related. Joins also let you select data from a table depending upon data from another table. Types of joins: INNER JOINs, OUTER JOINs, CROSS JOINs. OUTER JOINs are further classified as LEFT OUTER JOINS, RIGHT OUTER JOINS and FULL OUTER JOINS.

How can I enforce to use particular index?

You can use index hint (index=index_name) after the table name. SELECT au_lname FROM authors (index=aunmind)

What is sorting and what is the difference between sorting and clustered indexes?

The ORDER BY clause sorts query results by one or more columns up to 8,060 bytes. This will happen by the time when we retrieve data from database. Clustered indexes physically sorting data, while inserting/updating the table.

What are the differences between UNION and JOINS?

A join selects columns from 2 or more tables. A union selects rows.

What is the Referential Integrity?

Referential integrity refers to the consistency that must be maintained between primary and foreign keys, i.e. every foreign key value must have a corresponding primary key value
What is a deadlock?

Deadlock is a situation when two processes, each having a lock on one piece of data, attempt to acquire a lock on the other's piece. Each process would wait indefinitely for the other to release the lock, unless one of the user processes is terminated. SQL Server detects deadlocks and terminates one user's process.

What is a LiveLock?

A livelock is one, where a request for an exclusive lock is repeatedly denied because a series of overlapping shared locks keeps interfering. SQL Server detects the situation after four denials and refuses further shared locks. A livelock also occurs when read transactions monopolize a table or page, forcing a write transaction to wait indefinitely.

How to restart SQL Server in single user mode?

From Startup Options :- Go to SQL Server Properties by right-clicking on the Server name in the Enterprise manager. Under the 'General' tab, click on 'Startup Parameters'. Enter a value of -m in the Parameter.

Does SQL Server 2000 clustering support load balancing?

SQL Server 2000 clustering does not provide load balancing; it provides failover support. To achieve load balancing, you need software that balances the load between clusters, not between servers within a cluster.

What is DTC?

The Microsoft Distributed Transaction Coordinator (MS DTC) is a transaction manager that allows client applications to include several different sources of data in one transaction. MS DTC coordinates committing the distributed transaction across all the servers enlisted in the transaction.

What is DTS?

Microsoft? SQL Server? 2000 Data Transformation Services (DTS) is a set of graphical tools and programmable objects that lets you extract, transform, and consolidate data from disparate sources into single or multiple destinations.

What are defaults? Is there a column to which a default can't be bound?

A default is a value that will be used by a column, if no value is supplied to that column while inserting data. IDENTITY columns and timestamp columns can't have defaults bound to them.

What are the constraints ?

Table Constraints define rules regarding the values allowed in columns and are the standard mechanism for enforcing integrity. SQL Server 2000 supports five classes of constraints. NOT NULL , CHECK, UNIQUE, PRIMARY KEY, FOREIGN KEY.

What is Transaction?

A transaction is a sequence of operations performed as a single logical unit of work. A logical unit of work must exhibit four properties, called the ACID (Atomicity, Consistency, Isolation, and Durability) properties, to qualify as a transaction.

What is Isolation Level?

An isolation level determines the degree of isolation of data between concurrent transactions. The default SQL Server isolation level is Read Committed. A lower isolation level increases concurrency, but at the expense of data correctness. Conversely, a higher isolation level ensures that data is correct, but can affect concurrency negatively. The isolation level required by an application determines the locking behavior SQL Server uses. SQL-92 defines the following isolation levels, all of which are supported by SQL Server:
Read uncommitted (the lowest level where transactions are isolated only enough to ensure that physically corrupt data is not read).
Read committed (SQL Server default level). Repeatable read. Serializable (the highest level, where transactions are completely isolated from one another).

Saturday, 2 August 2014

Hadoop , Big Data Interview Questions

What is BIG DATA?

What is Hadoop?

Why the name ‘Hadoop’?

Why do we need Hadoop?

Can you give some examples of Big Data?

Can you give a detailed overview about the Big Data being generated by Facebook?

According to IBM, what are the three characteristics of Big Data?

How Big is ‘Big Data’?

How analysis of Big Data is useful for organizations?

Who are ‘Data Scientists’?

What are some of the characteristics of Hadoop framework?

Give a brief overview of Hadoop history.

Give examples of some companies that are using Hadoop structure?

What is the basic difference between traditional RDBMS and Hadoop?

What is structured and unstructured data?

What are the core components of Hadoop?

What is HDFS?

What are the key features of HDFS?

What is Fault Tolerance?

Replication causes data redundancy then why is is pursued in HDFS?

Since the data is replicated thrice in HDFS, does it mean that any calculation done on one node will also be replicated on the other two?

What is throughput? How does HDFS get a good throughput?

What is streaming access?

What is a commodity hardware? Does commodity hardware include RAM?

What is a Namenode?

Is Namenode also a commodity?

What is a metadata?

What is a Datanode?

Why do we use HDFS for applications having large data sets and not when there are lot of small files?

What is a daemon?

What is a job tracker?

What is a task tracker?

Is Namenode machine same as datanode machine as in terms of hardware?

What is a ‘block’ in HDFS?

What are the benefits of block transfer?

If we want to copy 10 blocks from one machine to another, but another machine can copy only 8.5 blocks, can the blocks be broken at the time of replication?

How indexing is done in HDFS?

If a data Node is full how it’s identified?

If datanodes increase, then do we need to upgrade Namenode?

Are job tracker and task trackers present in separate machines?

When we send a data to a node, do we allow settling in time, before sending another data to that node?

Does hadoop always require digital data to process?

On what basis Namenode will decide which datanode to write on?

Doesn’t Google have its very own version of DFS?

Who is a ‘user’ in HDFS?

Is client the end user in HDFS?

What is the communication channel between client and namenode/datanode?

What is a rack?

On what basis data will be stored on a rack?

Do we need to place 2nd and 3rd data in rack 2 only?

What if rack 2 and datanode fails?

What is a Secondary Namenode? Is it a substitute to the Namenode?

What is the difference between Gen1 and Gen2 Hadoop with regards to the Namenode?

What is MapReduce?

Can you explain how do ‘map’ and ‘reduce’ work?

What is ‘Key value pair’ in HDFS?

What is the difference between MapReduce engine and HDFS cluster?

Is map like a pointer?

Do we require two servers for the Namenode and the datanodes?

Why are the number of splits equal to the number of maps?

Is a job split into maps?

Which are the two types of ‘writes’ in HDFS?

Why ‘Reading‘ is done in parallel and ‘Writing‘ is not in HDFS?

Does Pig give any warning when there is a type mismatch or missing field?

What co-group does in Pig?

Can we say cogroup is a group of more than 1 data set?

What does FOREACH do?

What is bag?

Can you give us some examples how Hadoop is used in real time environment?

What is BloomMapFile used for?

What is PIG?

What is the difference between logical and physical plans?

Does ‘ILLUSTRATE’ run MR job?

Is the keyword ‘DEFINE’ like a function name?

Is the keyword ‘FUNCTIONAL’ a User Defined Function (UDF)?

Why do we need MapReduce during Pig programming?

Are there any problems which can only be solved by MapReduce and cannot be solved by PIG? In which kind of scenarios MR jobs will be more useful than PIG?

Can you give us some examples how Hadoop is used in real time environment?