To ensure that the correct data set is being opened, the system compares the data set name in the HDR1 label to the data set name specified by the user in the DD statement. This comparison is made on only the 17 least significant (rightmost) nonblank characters of the data set name (including 8 characters for the generation and version numbers if the data set is part of a generation data group). DFSMSrmm checks the full 44-character data set name if the previous data set name information is known to DFSMSrmm.

Processing is abnormally terminated if the comparison shows an incorrect data set name.