Mainframe Interview Questions

It is an MVS message that indicates the presence of a duplicate catalogue in the database. This problem can be fixed by removing one of the entries and then adding a new one.

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.

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

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.

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

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.

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.

Define new VSAM dataset allocated with more space.

Use IDCAMS to REPRO the old VSAM file to new VSAM dataset.

Use IDCAMS to ALTER / RENAME the old VSAM dataset to DELETE the old VSAM datset.

Use IDCAMS to ALTER / RENAME the new VSAM dataset to the name of the original VSAM dataset.