In this section, we will explore how to use JES2 (Job Entry Subsystem 2) and JES3 (Job Entry Subsystem 3) for troubleshooting JCL jobs. Both JES2 and JES3 are integral components of the z/OS operating system, responsible for managing job queues, scheduling, and output processing. Understanding how to leverage these systems can significantly aid in diagnosing and resolving issues in JCL jobs.

• JES2: Manages job processing in a single z/OS system. It handles job entry, scheduling, and output processing.
• JES3: Extends JES2 capabilities to manage job processing across multiple z/OS systems in a complex. It provides centralized control over job scheduling and resource allocation.

• $DA: Display active jobs.
• $DJ: Display job queue.
• $HASP: Display JES2 status.
• $P: Purge a job.
• $S: Start a job.

To display all active jobs in JES2, you can use the $DA command. This command provides a list of jobs currently being processed.

Explanation:

• $DA lists all active jobs, showing their job IDs, names, and statuses.

To display the job queue in JES2, use the $DJ command. This command shows all jobs waiting to be processed.

Explanation:

• $DJ lists all jobs in the queue, including their job IDs, names, and priorities.

If a job is stuck or needs to be removed from the queue, you can use the $P command followed by the job ID.

Explanation:

• $P JOB12345 purges the job with ID JOB12345 from the queue.

To manually start a job in JES2, use the $S command followed by the job ID.

Explanation:

• $S JOB12345 starts the job with ID JOB12345.

• Use the $DA and $DJ commands to identify jobs that are stuck or failing.
• Check the job status and error messages.

• Review the error messages associated with the job. These messages often provide clues about the nature of the problem.
• Use the JESMSGLG (JES Message Log) to find detailed error information.

• Based on the error messages, determine the appropriate corrective action. This might involve modifying the JCL, adjusting job parameters, or resolving resource conflicts.
• Use the $P command to purge problematic jobs if necessary.
• Restart jobs using the $S command after making corrections.

• Continuously monitor the job queue and active jobs using the $DA and $DJ commands.
• Ensure that jobs are progressing as expected and that no new errors have occurred.

1. Scenario: A job with ID JOB67890 is stuck in the queue and not progressing.
2. Steps:
   • Use the $DJ command to display the job queue and confirm the status of JOB67890.
   • Analyze the error messages associated with JOB67890 using the JESMSGLG.
   • Determine the cause of the issue (e.g., resource conflict, syntax error in JCL).
   • Purge the job using the $P JOB67890 command.
   • Correct the issue in the JCL and resubmit the job.
   • Use the $S JOB67890 command to start the job.
   • Monitor the job's progress using the $DA command.

Solution:

Explanation:

• $DJ displays the job queue to confirm the status of JOB67890.
• $P JOB67890 purges the stuck job.
• $S JOB67890 starts the corrected job.
• $DA monitors the active jobs to ensure JOB67890 is progressing.

In this section, we covered how to use JES2 and JES3 for troubleshooting JCL jobs. We explored common commands such as $DA, $DJ, $P, and $S, and provided practical examples and exercises to reinforce these concepts. By mastering these tools, you can effectively diagnose and resolve issues in your JCL jobs, ensuring smooth and efficient job processing.