The Free On-line Dictionary of Computing (30 December 2018):

DECtape

    A reel of magnetic tape about 4 inches
   in diameter and one inch wide.  Unlike today's macrotapes,
   microtape drivers allowed random access to the data, and
   therefore could be used to support file systems and even for
   swapping (this was generally done purely for hack value,
   as they were far too slow for practical use).  DECtape was a
   variant on LINCtape.

   In their heyday DECtapes were used in pretty much the same
   ways one would now use a floppy disk: as a small, portable
   way to save and transport files and programs.

   (1995-03-16)