Joined: 14 Jun 2006 Posts: 331 Location: Jacksonville, FL
REF tell the system to obtain volume serial numbers from an earlier DD statement. Your DD statement indicates you are trying to add the 75th dataset to a set of tapes that already has 74 datasets.
If two DD statements refer back to the same SYSEX175 DD statement, it is perfectly normal as long as the two DD statements are not in the same job step. If they were in the same step, there would be a contention issue between the two DD statements both trying to mount the same volume serial numbers.