Resolving the Instream Data Issue in JCL: Supplying Data to Cataloged PROC

Discover how to supply instream data to a cataloged PROC in JCL while following best practices and debugging tips. Join us to troubleshoot and learn step-by-step!
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Understanding and Supplying Instream Data to a Cataloged PROC in JCL

If you're working with Job Control Language (JCL) in a mainframe environment, you may encounter scenarios where you need to supply instream data to a cataloged procedure (PROC). This task is essential for executing jobs that require dynamic input directly specified in the JCL. In this post, we'll explore a common issue related to supplying instream data to a PROC and provide a straightforward solution.

The Problem: Can't See Instream Data in Job Output

In our example, we have a user attempting to replicate a scenario from the book "Murach’s OS/390 and z/os JCL." The user wants to supply an instream dataset in their invoking JCL to a procedure they are invoking. They faced the following challenges:

The expected data ("CIAO") is not visible in the job output.

Understanding why the instream data does not appear in the JCL listing can be confusing.

Here’s a brief overview of the initial code provided by the user:

Invoking Job

[[See Video to Reveal this Text or Code Snippet]]

Procedure Invoked

[[See Video to Reveal this Text or Code Snippet]]

Expected Output

The user expected to see the string "CIAO" in the job output but faced issues when modifying the DD name within the PROC.

The Solution: Modifying the Procedure for Instream Data

To resolve the issue, you can modify your PROC to handle instream data correctly. Here’s how to do it step by step:

Step 1: Change the PROC Definition

Change your procedure PROVA to resemble the following structure:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Rerun the Job

Run your first JCL again after modifying the PROC. You should now see the output containing the text "CIAO".

Step 3: Alternative Usage (Direct Instream Data)

If you wish to supply the instream data directly into another example, you can structure it as follows:

[[See Video to Reveal this Text or Code Snippet]]

Expected Outcome

After making these changes and rerunning the job, the string "CIAO" will be displayed in a separate output file as part of the job's output.

Additional Tips

JES Behavior: Remember that instream data is handled by the Job Entry Subsystem (JES), which separates it from the JCL when interpreting the jobs. Thus, the actual content won't be reproduced in the JCL listing.

Testing: It’s advisable to test in a controlled environment before deploying these changes in production.

Using DUMMY DD: Using DD DUMMY can be helpful in scenarios where you want to suppress output and focus on the logic.

With these modifications, you can successfully leverage instream data feeding into cataloged PROCs, resolving your initial challenge and enhancing your JCL knowledge. Happy coding!

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