ABACKUP considerations

If an instruction data set is specified in the aggregate group, DFSMSdss is used to write the instruction data set and the activity log data set (if DASD logging is specified), onto one file on a tape (or tapes). To save the volume serial numbers of this file in the control file, the instruction and activity log files are written before the control file. For coexistence with prior releases and for usability, the control file is the first file on the tape. Because of this necessity, the instruction and activity log files are written on a separate tape from the control file.

If an instruction data set is not specified in the aggregate group, the instruction data set name is left blank in the ABR record. A “DUMMY” instruction/activity log file is not created.