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.

MVS/ESA OpenEdition: Version of MVS/ESA announced February 1993 with support for POSIX standards. 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 lots of 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. Under OS/390, it became Unix System Services, and has kept that name under z/OS.