All The Useful Mainframe Interview Questions and Answers

Mainframe testing is somewhat similar to web-based testing.

1. What is the difference between HDAM and HIDAM databases?

HDAM database -    HIDAM database
HDAM databases do not have a separate index file. The key field in these files are passed through a randomizer and that places the record in its specific position in the database -    HIDAM databases have their own separate file indexes and they are based on the root segment. Each file has a piece of information about the pointer that shows the position of the data.

2. What is meant by referential integrity?
Referential integrity is a rule that states that there needs to be followed between the primary and foreign keys. This means that every foreign key needs to have a specific primary entry key

3. List the type of locks and explain each of them.

There are primarily three types of locks:

Shared lock - The shared lock allows two or more programs to be read from the locked space itself but it does not allow the viewer to modify it
Update lock - It is a relatively more lenient type of lock, it slows the program to be read and it can also be modified
Exclusive lock - As the name states, it restricts any user to access the locked space and its contents

4. What is INSPECT and what is it used for?
INSPECT is termed as a COBOL verb and it is used to discover the number of times a certain string shows up to supplant a certain segment of an information thing.

5. What is NEXT SENTENCE and CONTINUE unique?
NEXT SENTENCE is a code which handles the time frame and the stream of control into the statement. And the CONTINUE unique is responsible for the stream of control after the extension eliminator

6. What is meant by DRDA?
DRDA means Distributed Relational Database Architecture, It is essentially a protocol for connection for relational database processing which many vendor databases and the IBM database use.

This is one of the most important mainframe developer interview questions.

7. What is the term 'WHERE' for?
'WHERE' is a clause that is used which is meant to isolate a particular row or an element whenever it is used along with a relational statement

8. How do you create a LIKE table?
The LIKE table can be created It can be made by the use of the LIKE parameter in the statement CREATE. These tables are generally required for testing the production environment.

9. In a test environment, is there a need to run a runstats?
It is required to run a runstats because you have to clear the default values from the catalog columns. The existence of a default value in a column may result in an unexpected answer

10. Why do you need a secondary index in an IMS?
A secondary index is like an alternative path into any IMS database. It is a substitute path into any IMS database. It can be used as a file to acquire the required data.

11. Name the various types of tables spaces.
There are mainly three types of tablespaces

Simple
Segmented
Partitioned

12. Explain the meaning of SPUFI.
SPUFI stands for SQL Processing Using File Input. It is basically a tool driven by menus that the developers use to create objects in the database

13. What do you mean by an alias?
An alias is an alternative or a substitute to a synonym. They are created especially for distributed environments so that the developers can avoid using location qualifiers for tables or views.

14. Where is the VSAM KSDS placed?
The VSDM KSDS is placed at the BSDS. This question acts as a mainframe support interview question.

15. What is meant by an isolation level?
Isolation level is a degree by which the focused activation group is separated or isolated from the executed activation group at the same time is called an isolation level.

16. Name all the file-OPEN modes.
There are four file OPEN modes, they are:

INPUT
OUTPUT
EXTEND
I-O

17. Is the order of the WHEN clause important in an EVALUATE statement? Is the order of the WHEN clause significant in an EVALUATE statement?
Yes, the order of the WHEN clause is significant in an EVALUATE statement. It has to take place from the top to the bottom and thereby, the order of the values has an effect on the results and may impact the outcome

18. Are scope terminators compulsory? If they are, when?
Scope terminators are mandatory for EVALUATE statements and in-line PERFORMS. These are always declared with complete transparency to improve its readability

19. What do you mean by linkage section?
The linkage is a part of a program that maps to the specific data in the program's working storage.

A linkage section is an area where any shared data item is defined and declared.

20. Explain how you can characterize tables in COBOL.
The happens condition is used to characterize exhibits or tables in COBOL. The components of the table can be eluded by using INDEX or SUBSCRIPT

21. What is the usage of COMP fields in COBOL?
The COMP fields are usually used for the optimum utilization for speed and space handling for arithmetic operations

22. In which area will you utilize 88 level items in COBOL?

88 level items indicate restrictive factors and it helps in making choices for specific conditions in a program. You can use SET to increase the incentive for 88 level elements

23. Is it possible to move an alphanumeric incentive to a numeric field?
Yes, it is possible to move an alphanumeric incentive to a numeric field with a MOVE statement.

24. What is the difference between Delimited by size and Delimited by space?
When it comes to delimited by size, the delimiter is when you add up to the size of information in the field. When it comes to delimited by space, the space itself is the delimiter

25. What is meant by COMP-3 and what is it used for?
COMP-3 is used to share space and is a pressed decimal portrayal of information

26. Is it possible to move the alphanumeric variables to a numeric variable?
Yes, it is possible. If the field is used as part of the computation, you may face an information case problem (S0C7). This data provides a solution to COBOL queries with information development of many factors

27. Can Min or Max be used with alphanumeric data?
Yes, you can use MIN or MAX with alphanumeric information

28. What is meant by deadlock in DB2?
A deadlock is a situation when an independent process is contended for a reserved or the same resource of one another. -911 and -913 are the SQL codes for a deadlock.

29. What is meant by a bolt dispute?
A bolt dispute is said to happen when an excess of one protest asks for consent for its execution simultaneously. The DBD passage only allows one question at a time

30. Explain a linkage segment.
A linkage segment is a part of a program that maps to information things in the working stockpile of the program.