OPEN for Input

CA 1 compares the data set name specified in the DD statement with the corresponding data set name that is recorded for the volume in the TMC. If the data set names are identical, processing is allowed to continue; otherwise, the job is abended. This validity check is performed after the operating system has checked the 17-character data set name in the tape header record against the data set name requested in the DD statement. The validity check by CA 1 compares the complete 44-character data set name. After input has been authorized, the last used information is updated in the TMC.

This input data set name check, maintains the integrity of the TMC by preventing the wrong volume from being overwritten when there are duplicate VOLSER numbers. If an abend occurs, it usually indicates that a tape has been written on without the knowledge of CA 1. This can be caused by any of the following:

The standard MVS OPEN routines were bypassed.
The tape was written on outside the installation without being properly checked out-of-area.
The special CA 1 EXPDT keyword for nonresident tapes was used incorrectly.