If you have previously specified an instruction data set name in the aggregate group definition, or if the ABACKUP activity log is directed to DASD by using SETSYS ABARSACTLOGTYPE(DASD), then the optional instruction/activity log file is written to a different tape volume than the control and data files. See Creating an instruction data set.
The format of the instruction/activity log data set name is outputdatasetprefix.I.CnnVnnnn. This is the same outputdatasetprefix you previously specified in the aggregate group. See Defining an aggregate group.