JCL Realtime (Scenario based) Interview Questions (11 - 20)

11. How would you handle a situation where a JCL abends, and you need to restart it from a specific step?

If a JCL job abends, you can restart it from a specific step using the RESTART parameter.

  • Using the RESTART Parameter in the JOB Statement: Restart from a specific step by adding RESTART=stepname in the JOB statement. 
    //JOBSTEP JOB (ACCOUNT),'DESC',RESTART=STEP5
...
    In this example, the job will restart from STEP5. Make sure that the steps you are skipping do not affect the execution of the restarted step. If datasets or files were used in previous steps, they must be handled properly to avoid any conflicts.
  • Restarting with a Checkpoint (If Program Supports It): If the program supports checkpointing, specify it in the SYSIN or control card.
  • Using a JOB Scheduler (e.g., Control-M, CA-7): If using a scheduler, restart options can be defined there.

12. What would you do if a JCL job fails due to a missing dataset?

If a JCL job fails due to a missing dataset, follow these steps to resolve the issue:

  • Verify DISP Parameter Usage - Ensure the dataset is correctly defined in the DISP parameter:
    • If creating a new dataset, use: DISP=(NEW,CATLG,DELETE)
    • If the dataset should already exist, use: DISP=SHR
  • Manually Create the Missing Dataset - If the dataset is missing, allocate it using IEFBR14.
  • Recatalog an Uncataloged Dataset - If the dataset exists but is not cataloged, recatalog it using IDCAMS.

13. How would you handle a job that takes too long to execute due to excessive resource usage?

If a job is running too long, you can take the following actions:

  • Set a Time Limit Using the TIME Parameter - Restrict job or step execution time to prevent long-running jobs. //JOBNAME JOB ...,TIME=10
  • Optimize Program and SQL Queries - Review COBOL, PL/I, or SQL queries to improve efficiency.
  • Increase Region Size if Memory Is a Bottleneck - Allocate more memory to avoid excessive paging.
  • Break the Job Into Smaller Jobs or Parallel Execution - Split large datasets into smaller parts and process them separately.

14. How do you execute the same step multiple times in a single job?

You can execute the same step multiple times using the following methods:

  • Using a PROC with Different Parameters - Define a PROC and call it multiple times with different parameters.
  • Using the Utility - you can run utility multiple times in separate steps.
  • Manually Duplicating Steps - Copy the step and run it multiple times with different parameters.

15. How do you ensure that a specific step runs only if the previous step completes successfully?

You can control step execution using the following methods:

  • Using the COND Parameter - Runs a step only if the previous step does not fail. 
    //STEP2 EXEC PGM=PROG2,COND=(0,NE,STEP1)
  • Using IF/THEN/ELSE Logic - Allows complex conditions for execution.
  • Using a Job Scheduler - Tools like Control-M, CA-7 allow job dependencies based on return codes.

16. What would you do if a job needs to be executed on specific days of the week?

If a job needs to run only on specific days, you can schedule it using a scheduling tool such as CA-7, OPC, or Control-M. Within these tools, you can specify the days of the week when the job should be executed. It's important to note that JCL does not manage date-based scheduling itself; it relies on external schedulers for that function.

17. How would you handle a situation where a job requires exclusive access to a dataset?

To ensure exclusive access to a dataset during job execution, use the DISP=OLD parameter in the DD statement. This prevents other jobs from accessing the dataset while current job is running.

//DDNAME DD DSN=MY.DATA.SET,DISP=OLD

If another job tries to access the dataset at the same time, it will wait until the current executing job completes.

18. Write a JCL snippet to execute a COBOL program named 'MYPROG' with input and output datasets.

To execute a COBOL program named 'MYPROG' with input and output datasets, you would use the following JCL snippet: 

//MYJOB JOB (ACCT),'MATEPK',CLASS=A
//STEP1 EXEC PGM=MYPROG 
//INPUT DD DSN=MY.INPUT.DATASET,DISP=SHR 
//OUTPUT DD DSN=MY.OUTPUT.DATASET,
//          DISP=(NEW,CATLG,DELETE),
//          SPACE=(CYL,(1,1)),UNIT=SYSDA

19. Explain the use of the SYSOUT parameter in JCL.

The SYSOUT parameter is used to define the destination of the system output generated by the program or job step. It specifies the device class, the device number or name, and the output class.

20. Write a JCL to run a job that includes multiple steps, with the second step dependent on the success of the first.

To run a job with multiple steps where the second step depends on the success of the first, you would use the COND parameter to control the execution flow. For example,

//MYJOB JOB (ACCT),'MATEPK'
//STEP1 EXEC PGM=PROG1 
//STEP2 EXEC PGM=PROG2,COND=(0,NE,STEP1)