During a tape creation the USERID field is correctly referenced with the userid, but when the job ends, the field is overlaid by "CATALOG" ?
Release : 14.0
When a tape is created the USERID of the job is updated in the USERID field. If the tape is then cataloged the USERID is updated with CATALOG because the REALTIME catalog interface is updating the TMC for this entry. CA1 will always update the USERID with the information from the task to last modify the record.
Running a TMSAUDIT displays the information how and when the USERID was updated during the creation of the tape.
Something else to consider is the TMOKEYxx which permits to store the USERID into the USER field . More information about how this could be configurated can be find on TMOKEYxxx Option Table.