Use the EXITPGM parameter

The EXITPGM parameter can be used for various purposes.

To change the defaults used on the create commands submitted by option 3.
For example, if F4 (Prompt) is not used, the EXITPGM parameter could change one or more of the create commands to specify your own default requirements. If F4 is used, the EXITPGM parameter could submit the command as entered by the programmer (with no parameters changed).
To change parameters regardless of the programmer's use of F4.
This requires scanning the value of the &RQSDTA512 parameter (which is passed to the exit program) to see if it had already been used and substituting the required value.
To change other parameters on the Submit Job (SBMJOB) command.
For example, the user parameter of the Submit Job (SBMJOB) command could be changed to specify the value of the job description instead of the value of *CURRENT. It is also possible to retrieve the values of one or more job attributes by using the Retrieve Job Attributes (RTVJOBA) command, entering the attributes as specific values.
To enforce local programming conventions.
For example, if you have a naming standard that requires all physical files to be named with 7 characters and end with a P, the exit program could reject any attempt to use the Create Physical File (CRTPF) command with a name that did not follow this standard.