Job Control Language (JCL) is a crucial scripting language used in IBM mainframe environments to instruct the system on how to execute batch jobs. Whether you’re a mainframe developer, system programmer, or tester, mastering JCL interview questions is essential for securing a role in mainframe computing.
In this guide, we’ll cover the top 20 JCL interview questions with detailed answers to help you crack your next technical interview.
What is JCL and Why is it Used?
Answer:
JCL (Job Control Language) is a scripting language used in IBM mainframe environments to define and control batch jobs. It specifies:
- Programs to execute
- Input/output files
- System resources required
Key Features of JCL:
- Defines job steps, datasets, and execution priorities.
- Supports conditional execution using
IF-THEN-ELSElogic. - Works with utilities like SORT, IEBGENER, IDCAMS.
20 Most Common JCL Interview Questions and Answers
1. What are the Basic JCL Statements?
Answer:
The three main JCL statements are:
- JOB Statement – Identifies the job (e.g.,
//JOB1 JOB …). - EXEC Statement – Specifies the program to execute (e.g.,
//STEP1 EXEC PGM=COBOLPGM). - DD Statement – Defines input/output datasets (e.g.,
//INPUT DD DSN=EMP.DATA).
2. What is a JOBLIB and STEPLIB in JCL?
Answer:
- JOBLIB – Specifies a library for all job steps.jclCopyDownload//JOBLIB DD DSN=PROD.LOADLIB,DISP=SHR
- STEPLIB – Specifies a library for a specific step.jclCopyDownload//STEP1 EXEC PGM=COBOLPGM //STEPLIB DD DSN=DEV.LOADLIB,DISP=SHR
3. What is the Difference Between DISP=SHR and DISP=OLD?
Answer:
- DISP=SHR – Dataset is shared (multiple jobs can read).
- DISP=OLD – Dataset is locked (exclusive access).
4. How to Pass Parameters to a COBOL Program in JCL?
Answer:
Use the PARM keyword in the EXEC statement:
//STEP1 EXEC PGM=COBOLPGM,PARM='123,ABC'
5. What is a COND Parameter in JCL?
Answer:
The COND parameter controls job step execution based on return codes:
//STEP2 EXEC PGM=PGM2,COND=(4,LT,STEP1)
(Executes only if STEP1’s return code is less than 4.)
6. What is a GDG (Generation Data Group)?
Answer:
A GDG is a collection of chronologically related datasets. Example:
//OUTPUT DD DSN=MY.GDG(+1),DISP=(NEW,CATLG)
7. How to Concatenate Datasets in JCL?
Answer:
Use multiple DD statements:
//INPUT DD DSN=FILE1,DISP=SHR // DD DSN=FILE2,DISP=SHR
8. What is SYSIN and SYSOUT in JCL?
Answer:
- SYSIN – Input data stream (e.g.,
//SYSIN DD *). - SYSOUT – Output destination (e.g.,
//SYSOUT DD SYSOUT=*).
9. How to Skip a Job Step in JCL?
Answer:
Use COND=ONLY or COND=EVEN:
//STEP2 EXEC PGM=PGM2,COND=ONLY
10. What is IEBGENER Utility in JCL?
Answer:IEBGENER copies datasets:
//STEP1 EXEC PGM=IEBGENER //SYSUT1 DD DSN=INPUT.FILE,DISP=SHR //SYSUT2 DD DSN=OUTPUT.FILE,DISP=(NEW,CATLG) //SYSPRINT DD SYSOUT=* //SYSIN DD DUMMY
11. What is the Purpose of IDCAMS in JCL?
Answer:IDCAMS is used for VSAM dataset operations (create, delete, listcat):
//STEP1 EXEC PGM=IDCAMS //SYSPRINT DD SYSOUT=* //SYSIN DD * DELETE MY.VSAM.CLUSTER /*
12. How to Handle Abends in JCL?
Answer:
Use ABEND codes and RETRY parameters:
//STEP1 EXEC PGM=PGM1 //STEP2 EXEC PGM=PGM2,COND=EVEN
13. What is a RESTART Parameter in JCL?
Answer:RESTART allows a job to resume from a specific step:
//JOB1 JOB RESTART=STEP3
14. How to Comment in JCL?
Answer:
Use //* for comments:
//* THIS IS A COMMENT
15. What is a NOTIFY Parameter in JCL?
Answer:NOTIFY sends job completion alerts:
//JOB1 JOB NOTIFY=&SYSUID
16. What is the Difference Between JCL and REXX?
Answer:
- JCL – Controls batch jobs.
- REXX – A scripting language for automation.
17. How to Use INCLUDE Statement in JCL?
Answer:INCLUDE adds predefined JCL:
//JCLLIB ORDER=(PROD.JCL) //STEP1 EXEC PGM=PGM1 //INCLUDE MEMBER=COMMONJCL
18. What is a Symbolic Parameter in JCL?
Answer:
Symbolic parameters allow dynamic values:
//JOB1 JOB &JOBNAME
19. How to Submit a JCL Job Programmatically?
Answer:
Use IEFBR14 (a dummy program) or IKJEFT01 (TSO command).
20. What is a PROC in JCL?
Answer:
A PROC (Procedure) is a reusable JCL block:
//MYPROC PROC //STEP1 EXEC PGM=PGM1 // PEND
People Also Ask
Q1. Is JCL still used in 2024?
Yes, JCL is still widely used in mainframe environments for batch processing.
Q2. What is the alternative to JCL?
Modern alternatives include z/OSMF workflows and Python scripting for automation.
Q3. How to debug JCL errors?
Check JOBLOG (SPOOL) for error codes like JCL ERROR or SOC7 ABEND.
Conclusion
Mastering JCL interview questions is essential for mainframe professionals. This guide covers everything from basic syntax to advanced utilities like IDCAMS and IEBGENER.
Need more help? Refer to IBM’s JCL Documentation.