(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)