The problem:

From 2.4 on it is possible to set variables (SETPARM) lasting for POWER-JOB duration and for SYSTEM duration. While with power-job duration variables this might not be a problem, but for system wide variables, there is no way to list what is defined nor a way to delete a specific variable.

The solution:

With SYSVAR you get a program (with source), that can list or delete a system-variable.
JCL how to use it is included.

The program is written with relative and immediate instructions and does not have a base-register for the code (but for the data-areas). If your CPU does not have these instructions, you can easy change the source to use the old ones.

Contact me for further questions.

Download the program.