, your terminology seems somewhat confused. If indeed your job is running a COBOL/DB2 via background, then I would expect PARMLIB(CPRC995Z) to contain something like:
RUN PROGRAM(BAR) PLAN(BAR) PARMS('P1 P2')
In which case your modification of PARMLIB(PARM1) in STEP1 would have no effect. To the left, the assignment of PARMLIB(PARM) to the file JOBDATA suggests that it contains control cards, not parameters...but of course the program would actually have to open and read that file. Can you verify for us which is the case?
"You have sat too long for any good you have been doing lately ... Depart, I say; and let us have done with you. In the name of God, go!" -- what I say to a junior programmer at least once a day