/sys$common/syshlp/HELPLIB.HLB  —  SET  MAGTAPE  Qualifiers  /MEDIA_FORMAT
       /MEDIA_FORMAT=[NO]COMPACTION

    Controls whether data records are automatically compacted and
    blocked together on a TA90E tape drive. Data compaction and
    record blocking increase the amount of data that can be stored
    on a single tape cartridge.

    Note that once data compaction or noncompaction has been selected
    for a given cartridge, that same status applies to the entire
    cartridge.
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