Was that before tape catalogs and volume labels? That was well before my time. In the OS/MVS environment I was in in the 80s, the job's JCL would identify a d

Was that before tape catalogs and volume labels? That was well before my time. In the OS/MVS environment I was in in the 80s, the job's JCL would identify a data set and a relative version number (+1 when creating, 0 for current, -1 for its predecessor, etc.), then the tape catalog would look up the volume number, which was written on the tape case itself (and usually correct). If the operator mounted a wrong tape (either wrong dataset or version), the tape would be kicked off and you'd be prompted again ("you dummy humans can't even handle unpacked decimal?!") It was typical that backup copies be made via an additional DD pass.