VSAM

from The Free On-line Dictionary of Computing (8 July 2008)

Virtual Storage Access Method
Virtual Sequential Access Method
VSAM

   <database> (VSAM) An {IBM} disk file storage scheme first used
   in {S/370} and virtual storage.  VSAM comprises three access
   methods: {Keyed Sequenced Data Set} (KSDS), {Relative Record
   Data Set} (RRDS), and {Entry Sequenced Data Set} (ESDS).

   Both {IMS/DB} and {DB2} are implemented on top of VSAM and use
   its underlying data structures.

   ["Storage" or "Sequential"?]

   (2002-07-26)

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

VSAM
       Virtual Sequential Access Method (SAM)

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

VSAM
       Virtual Storage Access Method