In this section, we will explore the concept of temporary data sets in JCL. Temporary data sets are used for intermediate storage during the execution of a job and are deleted automatically when the job completes. They are particularly useful for passing data between steps within the same job.

1. Definition: Temporary data sets are data sets that exist only for the duration of the job and are deleted once the job completes.
2. Naming Convention: Temporary data sets are identified by names that start with two ampersands (&&).
3. Scope: They are accessible only within the job in which they are created.

To define a temporary data set in JCL, you use the DD statement with a name that starts with &&. Here is the basic syntax:

Let's look at a practical example where we create a temporary data set and use it in subsequent steps.

1. STEP1:

   • TEMPDS: Defines a temporary data set named &&TEMP. The DISP=(NEW,PASS) parameter indicates that the data set is newly created and will be passed to the next step.
   • UNIT=SYSDA: Specifies the device type.
   • SPACE=(CYL,(1,1)): Allocates space for the data set.
   • DCB=(RECFM=FB,LRECL=80,BLKSIZE=800): Defines the data control block parameters.

2. STEP2:

   • INPUT: References the temporary data set &&TEMP created in STEP1. The DISP=(OLD,DELETE) parameter indicates that the data set is to be used as an existing data set and will be deleted after this step.

Task: Write a JCL job that creates a temporary data set in the first step and uses it in the second step.

Solution Explanation:

• STEP1: Creates a temporary data set &&TEMP with the necessary parameters.
• STEP2: Uses the temporary data set &&TEMP and deletes it after use.

Task: Modify the previous job to add a third step that reads the temporary data set again.

Solution Explanation:

• STEP1: Creates the temporary data set &&TEMP.
• STEP2: Uses the temporary data set &&TEMP and passes it to the next step.
• STEP3: Reads the temporary data set &&TEMP again and deletes it after use.

• Incorrect DISP Parameter: Ensure that the DISP parameter is correctly set to PASS when passing the data set between steps.
• Naming Convention: Always start the name of a temporary data set with &&.
• Scope Limitation: Remember that temporary data sets are only accessible within the job they are created in.

Temporary data sets are a powerful feature in JCL for managing intermediate data within a job. By understanding how to create, use, and manage these data sets, you can write more efficient and organized JCL jobs. In the next section, we will delve into referencing data sets, which will further enhance your ability to manage data within your JCL jobs.