MVS/ESA
MVS/ESA: MVS Enterprise System Architecture. Version of MVS, first introduced as MVS/SP Version 3 in February 1988. Replaced by/renamed as OS/390 late 1995 and subsequently as z/OS.
MVS/ESA OpenEdition: upgrade to Version 4 Release 3 of MVS/ESA announced February 1993 with support for POSIX and other standards. While the initial release only had National Institute of Standards and Technology (NIST) certification for Federal Information Processing Standard (FIPS) 151 compliance, subsequent releases were certified at higher levels and by other organizations, e.g. X/Open and its successor, The Open Group. It included about 1 million new lines of code, which provide an API shell, utilities, and an extended user interface. Works with a hierarchical file system provided by DFSMS (Data Facility System Managed Storage). The shell and utilities are based on Mortice Kerns' InterOpen products. Independent specialists reckon it was over 80% open systems-compliant—more than most Unix systems. DCE2 support announced February 1994, and many application development tools in March 1995. Mid 1995 IBM started to stop referring to OpenEdition as a separate entity, as all the open features became a standard part of vanilla MVS/ESA SP Version 5 Release 1. Under OS/390, it became UNIX System Services, and has kept that name under z/OS.
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