One of the important use of proc is, we can reuse it. So, if we want to make any changes in the proc, we can make those by overriding the parameters in the JCL.
The below example gives pretty good idea on COND and Restart:
//JOBSTEP EXEC PROC=TEST,COND.PROCSTP4=(8,GT)
When we give COND on Step, it validates with all previous steps return codes.
The above piece of code will do – Restarts Procstp2, and, COND parameter is overridden for Procstp4.
Keep reading my all posts on JCL COND parameter.