When checking in external volumes, the volser of a volume being checked may be identical to the volser of a volume already in the Media Database. This creates a problem because the volser must be a unique identifier of a volume in the Media Database.
To solve this problem, Control-M/Tape stores volume identification information in the following way:
When a volume is checked in, the user assigns a new unique volser to the volume. The new unique volser is recorded in the VOLSER field of the volume record in the Media Database.
The original volser value (that matches the Standard Label of the volume) is recorded in the SL-NAME field in the volume record in the Media Database.
From this point on, whenever this checked-in volume is accessed, the new volser is used to identify the volume (including MVS Catalog if cataloged, JCL references to the volume, and so on).
