From The Free On-line Dictionary of Computing (8 July 2008) [foldoc]:
Multiple Virtual Storage
MVS
MVS/ESA
MVS/OE
MVS/Open Edition
MVS/SP
MVS/XA
<operating system> (MVS) Release 2 of OS/VS2, called MVS
because it had multiple 16 MB virtual address spaces, in
contrast to SVS. MVS ran on the IBM 390 series
mainframes. It became MVS/SP, then MVS/XA (with 31-bit
addressing) and then MVS/ESA.
MVS/Open Edition (MVS/OE), aimed at the growing open systems
market, added TCP/IP and Unix support in an MVS address
space, allowing users to run IBM, CICS-type applications,
batch applications and Unix.
MVS/ESA was repackaged as OS/390 as a marketing exercise but
it's basically the same thing.
Version: 5.1.
[Features? Dates?]
(1999-01-20)