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

Record Management Services

    (RMS) Procedures in the VMS operating
   system that programs call to process files and records
   within files.  RMS allows programs to issue GET and PUT
   requests at the record level (record I/O) as well as read and
   write blocks (block I/O).  VMS RMS is an integral part of
   the system software; its procedures run in executive mode.

   (2003-11-11)