Mainframe Interview Questions

Q:

What COBOL construct is the COBOL II EVALUATE meant to replace?

Answer

EVALUATE can be used in place of the nested IF THEN ELSE statements.

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Q:

How can we distinguish between an online and batch program in IMS environment?

Answer

If in application program IO-PCB is there then it is a online program. In ENTRY statement IO-PCB must be listed first and then DB-PCB.

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Q:

What is a DB2 bind?

Answer

A DB2 bind is a process that builds an access path to DB2 tables. 

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Q:

What are different file OPEN modes available in COBOL?

Answer

Open for INPUT, OUTPUT, I-O, EXTEND.


1.INPUT : for read only purpose


2.OUTPUT : for write only purpose


3.EXTEND : for appending records


4.I-O : for read and write(using EXTEND) purpose

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Q:

What is RUNSTATS?

Answer

A DB2 utility used to collect statistics about the data values  in tables which can be used   by the optimizer to decide the access path. It also collects statistics used for space   management. These statistics are stored in DB2 catalog tables.

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Q:

Difference between Embeded SQL and Dynamic SQL?

Answer

Static (embedded) SQL:


1.In static SQL how database will be accessed is predetermined in the embedded SQL statement.


2.It is more swift and efficient.


3.SQL statements are compiled at compile time.


4.Parsing, validation, optimization, and generation of application plan are done at compile time.


5.It is generally used for situations where data is distributed uniformly.


6.EXECUTE IMMEDIATE, EXECUTE and PREPARE statements are not used.


7. It is less flexible 


 


Dynamic (interactive) SQL:


1.In dynamic SQL, how database will be accessed is determined at run time.


2.It is less swift and efficient.


3.SQL statements are compiled at run time.


4.Parsing, validation, optimization, and generation of application plan are done at run time.


5.It is generally used for situations where data is distributed non-uniformly.


6.EXECUTE IMMEDIATE, EXECUTE and PREPARE statements are used.


7.It is more flexible.

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Q:

What is REORG? When it is used?

Answer

REORG reorganizes data on physical storage to reclutser rows, positioning overflowed rows in their proper sequence, to reclaim space, to restore free space. It is used after heavy updates, inserts and delete activity and after segments of a segmented tablespace have become fragmented.

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Q:

What is a cursor ? Why should it be used in DB2?

Answer

Cursor is a programming device that allows the SELECT to find a set of rows but return them one at a time. Cursor should be used because the host language  can deal with only one row at a time.

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