You Better Be Able to Answer These 18 Mainframe Interview Questions

mainframe interview questions and answers

Top positions are incredibly competitive today, so you need to be sure that you’re capable of answering expert mainframe interview questions. Even with the unprecedented need for applicants with mainframe experience, recruiters are still incredibly picky when it comes to finding out if candidates are truly qualified.

It’s not just about standing out. If you don’t know these mainframe interview questions and answers, you may not even be considered. Take a look at these technical interview questions and see how many you can answer. If you aren’t nailing it, then mainframe courses could be the right investment for your professional development.

  1. When’s the Right Time to Choose EXIT PROGRAM vs. GOBACK or STOP RUN in Cobol?

In Cobol, EXIT PROGRAM is used specifically to exit a program that has been called by a separate program, as opposed to GOBACK, which returns control to the calling program, and STOP RUN, which halts the present work unit and gives control back to the OS.

  1. What’s the Difference Between HIDAM and HDAM Databases?

HIDAM and HDAM are both hierarchical direct databases. HIDAM databases have a separate index file based on the root segment, while HDAM databases instead use a randomizer to place records in particular locations in the database.

  1. What Are the Three Types of Table Spaces?

The answer to this mainframe interview question is that the three types of tables spaces are:

  • Simple
  • Segmented
  • Partitioned


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  1. What Are Foreign Keys?

Foreign keys are the properties of a particular table that have matching entries to a primary key in a separate table. This forms a relationship between the two separate tables.

  1. What Does DRDA Mean?

DRDA is Distributed Relational Database Architecture. It’s the connection protocol used in IBM mainframes and other vendor databases, containing the set of rules used to communicate between applications and a DBMS distant relation.

  1. What Is a Linkage Section?

A linkage section is a part of a program that is called and maps to data items in the working storage of the program. The linkage sections are where shared items can be declared and defined.

  1. If a System Error Occurs When Processing a VSAM File and Causes It to Be Unusable, What Could You Do?

In VSAM, you can run VERIFY to check and fix any VSAM files that haven’t closed properly following an error. VERIFY will add correct End-of-Data records to the file, resolving the issue.

  1. How Can You Differentiate Between a STATIC or DYNAMIC CALL?

If the program name is mentioned explicitly in the CALL articulation, then it is a STATIC call. If a working stockpile variable is alluded to in the CALL explanation, then it is a DYNAMIC CALL.

  1. What Are the Four Divisions in a COBOL Program?

The four divisions in a COBOL program are:

  • The identification division
  • The environment division
  • The data division
  • The procedure division

When Is the Evaluate Statement Useful in COBOL?


Mainframe Interview Questions


Evaluate provides a better solution for checking multiple conditions than using IF-ELSE. Using EVALUATE, a single condition can be used to check multiple conditions, which is more effective and cleaner than nested IF-ELSE statements.

  1. What’s the Difference Between INCLUDE and COPY?

While they both help extend design in a program, INCLUDE is extended at PRE-COMPILATION to organize itself, which is why all DCLGEN individuals are extended using INCLUDE.

  1. What’s the Difference Between INPUT and OUTPUT File OPEN Modes?

INPUT mode is used for existing files and only allows for reading the file and not any other operations on the file. OUTPUT mode is for inserting records in files. If a sequential file is used and is holding some records, the existing records will be deleted, and then the new records will be inserted.

  1. What Are the Three Types of Locks, and What Are They For?

The three types of locks are shared, update, and exclusive. Shared lock permits two or more programs to read the locked space but doesn’t allow them to change it. Update lock allows the program to both read and change the locked space. Exclusive lock restricts the access of all users to the locked space.

  1. When Would It Be Appropriate to Use a Binary Search?

While a binary search may be faster than a linear search, the array needs to be sorted before the search. Binary search can be useful in solving problems like finding the next smallest or next largest element in an array.


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  1. What Is the Function of DBCTL?

DBCTL is used to access the IMS filed for CICS transactions. These are fixed in the DBTCL for accessing files. When an IMS call is generated by the CICS program, the DBCTL is carried by the DBCTL, and a reply is sent as the outcome.

  1. What Is a Clustered Index?

In a clustered index, the columns are maintained in the same sequence as the rows until there’s free space in memory. DB2 then processes the table in the given order immediately.

  1. Why Are COMMITS Coded in Batch Programs?

COMMIT statements release locks as required for each unit of work, then permitting a new unit of work. If COMMITS are not coded, the program will have to go back to the inserts made over the entire course of running the program instead of just going back a few inserts to the most recent COMMIT.

  1. In What Way Are Composite and Multiple Indexes Different?

Multiple indexes are two indexes, one each for columns of the same table. A composite index is just one index that consists of combined values for two columns.

Other Mainframe-Experienced Interview Questions to Watch Out For

If you’ve gotten most of these IBM mainframes interview questions right so far, then you may think you’re a sure thing for any technical position. However, while mainframe interview questions for experienced candidates are an essential part of recruiting and hiring, they aren’t everything.

Keep in mind that mainframe interview questions and answers are just one piece of the puzzle—the rest focuses on questions about yourself, your experience, and how you approach problem-solving. 

Try to think of a few specific examples of challenges you’ve dealt with to answer these mainframe experience interview questions. You don’t want to be caught trying to remember them on the spot!

Answer Mainframe Interview Questions Like a Pro


mainframe experience interview questions


So, how did you do? If you struggled with some of these questions, that’s perfectly understandable. However, when it comes to finding a high-level position, you could likely stand to improve your knowledge base. With the increasing demand for experienced developers, investing in yourself today could show considerable returns.

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Published August 30, 2022