Mainframe Interview Questions

Q:

What is ENQ in CICS ?

Answer

If any one want to restrict Trans-ID to single user, enter trans-id with ENQ. It won't allow any one else to use the same trans-id.

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Q:

What do you accomplish by GROUP BY ... HAVING clause?

Answer

GROUP BY partitions the selected rows on the distinct values of the column on which you group by. HAVING selects GROUPs which match the criteria specified

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Q:

How can record locking be achieved in those DB2 versions which do not support it?

Answer

It can be done by setting the record length’s size to more than half of the page’s size.

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Q:

What is the difference between the INTO and the SET option in the EXEC CICS RECEIVE MAP command?

Answer

The INTO option moves the information in the TIOA into the reserved specified area, while the SET option simply returns the address of the TIOA to the specified BLL cell or address of a linkage-section.


 

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Q:

How does DB2 use multiple table indexes?

Answer

DB2 use the multiple indexes to satisfy multiple predicates in a SELECT statement that are joined by an AND or OR.

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Q:

What does it mean if the null indicator has -1, 0, -2?

Answer

 -1 indicates the field is null


 0 indicates the field is not null


 -2 indicates the field is truncated

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Q:

Why is free space left in KSDS Dataset?

Answer

While allocating KSDS Datasets, free space is declared at regular intervals at the time of initial loading. This is done because this free space is utilized for keeping the data arranged in sequence physically, even though inserted randomly.

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Q:

My SQL statement SELECT AVG(SALARY) FROM EMP yields inaccurate results. Why?

Answer

Because SALARY is not declared to have NULLs and the employees for whom the salary is not known are also counted.


 

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