Symbolic parameters in JCL are placeholders that can be replaced with actual values when the JCL is executed. They are particularly useful in procedures (PROCs) to make them more flexible and reusable. This section will cover the basics of symbolic parameters, how to define them, and how to use them in your JCL jobs.

1. Definition: Symbolic parameters are defined within procedures and are replaced by actual values when the procedure is invoked.
2. Syntax: Symbolic parameters are denoted by an ampersand (&) followed by the parameter name.
3. Substitution: The actual values for symbolic parameters are provided in the JCL that calls the procedure.

Symbolic parameters are defined in the procedure using the & symbol. Here is an example of a procedure with symbolic parameters:

In this example:

• P1 and P2 are symbolic parameters.
• DEFAULT1 and DEFAULT2 are default values for these parameters.

When you call a procedure, you can override the default values of symbolic parameters. Here is how you can do it:

In this example:

• The procedure MYPROC is called.
• The symbolic parameters P1 and P2 are replaced with MY.DATA.SET1 and MY.DATA.SET2, respectively.

Let's look at a more detailed example to understand how symbolic parameters work in a real-world scenario.

In this example:

• The procedure BACKUP is defined with symbolic parameters BKPDSN and BKPUNIT.
• When the procedure is called in MYJOB, the symbolic parameters are replaced with USER.BACKUP.DSN and TAPE.

1. Define a procedure named COPYPROC that copies data from one data set to another. Use symbolic parameters for the input and output data set names.
2. Call the procedure in a JCL job, providing actual values for the symbolic parameters.

Solution

Procedure Definition:

JCL Calling the Procedure:

1. Modify the COPYPROC procedure to use different default values for the symbolic parameters.
2. Call the procedure without overriding the symbolic parameters to see the default values in action.

Solution

Modified Procedure Definition:

JCL Calling the Procedure:

In this case, the default values NEW.DEFAULT.INPUT.DSN and NEW.DEFAULT.OUTPUT.DSN will be used.

• Mistake: Forgetting to use the & symbol when defining symbolic parameters.
  • Tip: Always start symbolic parameter names with &.
• Mistake: Not providing values for symbolic parameters when calling the procedure.
  • Tip: Ensure you provide values for all required symbolic parameters, or verify that the default values are appropriate.

Symbolic parameters are a powerful feature in JCL that enhance the flexibility and reusability of procedures. By understanding how to define and use symbolic parameters, you can create more dynamic and adaptable JCL jobs. Practice defining and using symbolic parameters to become proficient in this essential JCL concept.