(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)