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Mainframe Developer interview questions & mock practice

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What interview questions are asked for a Mainframe Developer?

A Mainframe Developer interview in 2026 runs across 4 rounds — cobol fundamentals, jcl and utilities, db2 and data, behavioural / project. Below are the most-asked Mainframe Developer interview questions and a focused prep plan. Rehearse every answer out loud with the free timed practice below before the real one.

  • COBOL
  • JCL
  • DB2
  • VSAM
  • CICS
  • SQL
  • File-AID
  • Debugging

Free interview practice · Mainframe Developer

Practise your Mainframe Developer interview now — free

Step through the 12 most-asked Mainframe Developer questions one at a time, under a timer, just like the real thing. Jot your answer, then reveal what a strong answer covers. No signup needed to practise.

Interview rounds

The Mainframe Developer interview process

COBOL, JCL, DB2, VSAM and CICS — the legacy enterprise skills tested for mainframe developer roles at Indian banks, insurers and large IT services companies.

1. COBOL fundamentals

COBOL divisions, data types, file handling and program structure.

2. JCL and utilities

JCL syntax, job steps, GDG and utilities like SORT and IEBGENER.

3. DB2 and data

Embedded SQL, cursors, DB2 concepts and VSAM or CICS basics.

4. Behavioural / project

Maintenance work, debugging abends and working in legacy systems.

Most-asked questions

Most-asked Mainframe Developer interview questions

12 of the questions Mainframe Developer candidates are asked most often in India. Practise answering each one out loud in the timed practice above.

  1. 1. What are the four divisions of a COBOL program and what does each do?
  2. 2. What is the difference between COMP, COMP-1, COMP-2 and COMP-3 in COBOL?
  3. 3. What is the difference between a static call and a dynamic call in COBOL?
  4. 4. What is the difference between SEARCH and SEARCH ALL?
  5. 5. What is a GDG and why is it used in JCL?
  6. 6. What is the difference between DISP=NEW, DISP=OLD and DISP=SHR in JCL?
  7. 7. What is the difference between a primary and a secondary index in VSAM?
  8. 8. What is a cursor in DB2 and when do you use it?
  9. 9. What is the difference between an S0C7 and an S0C4 abend and how do you debug them?
  10. 10. What is the difference between DELETE and TRUNCATE in DB2?
  11. 11. What is the difference between pseudo-conversational and conversational programming in CICS?
  12. 12. Describe a production abend you debugged and how you fixed the root cause.
How to prepare

How to prepare for your Mainframe Developer interview

Be solid on COBOL fundamentals including divisions, data types, the difference between COMP variants, and table handling with OCCURS.

Know JCL thoroughly, including job steps, DISP parameters, GDGs and common utilities like SORT, IEBGENER and IDCAMS.

Practise embedded SQL in COBOL with DB2, especially cursors, SQLCODE handling and join queries.

Understand how to read and debug common abends such as S0C7 and S0C4 using dumps, since maintenance roles test this heavily.

Prepare examples from real maintenance or enhancement work, including how you debugged a production issue under time pressure.

Practise other roles

Interview prep guides

Mainframe Developer interview — FAQs

What questions are asked in a Mainframe Developer interview?

Common Mainframe Developer interview questions include: What are the four divisions of a COBOL program and what does each do? What is the difference between COMP, COMP-1, COMP-2 and COMP-3 in COBOL? What is the difference between a static call and a dynamic call in COBOL? What is the difference between SEARCH and SEARCH ALL? Interviews usually run across 4 rounds — COBOL fundamentals, JCL and utilities, DB2 and data, Behavioural / project. Practise them with the free timed practice on this page.

How many rounds are in a Mainframe Developer interview?

A typical Mainframe Developer interview has 4 rounds: COBOL fundamentals (COBOL divisions, data types, file handling and program structure.); JCL and utilities (JCL syntax, job steps, GDG and utilities like SORT and IEBGENER.); DB2 and data (Embedded SQL, cursors, DB2 concepts and VSAM or CICS basics.); Behavioural / project (Maintenance work, debugging abends and working in legacy systems.).

How do I prepare for a Mainframe Developer interview?

To prepare for a Mainframe Developer interview: Be solid on COBOL fundamentals including divisions, data types, the difference between COMP variants, and table handling with OCCURS. Know JCL thoroughly, including job steps, DISP parameters, GDGs and common utilities like SORT, IEBGENER and IDCAMS. Practise embedded SQL in COBOL with DB2, especially cursors, SQLCODE handling and join queries. Then rehearse every question out loud with the timed practice on this page before the real thing.

What skills do I need for a Mainframe Developer role?

Core Mainframe Developer skills tested in interviews include COBOL, JCL, DB2, VSAM, CICS, SQL, File-AID, Debugging. OnJob shows you exactly which of these skills stand between you and a 100% match on every live Mainframe Developer job.

Is the Mainframe Developer mock interview practice free?

Yes. The questions, the answer guidance and the timed practice on this page are free and need no signup. With a free OnJob account you can also take timed role tests and free certification tests. Personalised AI role and skill tests are part of the paid plans.

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