by steve-myers » Sun Aug 12, 2012 7:34 am
In terms of a tape management system, a "scratch tape" is a tape volume available for reuse.
Tape librarians run, usually at least once a day, jobs that analyze the tape catalog looking for tape volumes that have "expired," e.g. tape volumes containing datasets that are no longer required. The rules used by the tape management system are complex - far to complex to discuss here - to determine this status. JCL requests a "scratch tape" by not specifying a volume serial. The list of new scratch tapes is used by the tape librarians to place the scratch tapes in special racks for tapes that are manually mounted, and to automated tape library controllers so the tape library knows which tapes it can mount.