| UNIX System Services | |
|---|---|
| Developer | IBM |
| OS family | UNIX -POSIX |
| Working state | Current |
| Source model | Closed source |
| Initial release | 1998; 27 years ago (1998)[1] (Name changed fromOpenEdition toOS/390 UNIX System Services) |
| Latest release | Version 3.1 (V3R1) / September 29, 2023; 2 years ago (2023-09-29) |
| Marketing target | Enterprise / Mainframes |
| Available in | English and most other languages |
| Supported platforms | z/Architecture |
| License | Proprietary |
| Official website | z/OS UNIX System Services |
| History of IBM mainframe operating systems |
|---|
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z/OS UNIX System Services (z/OS UNIX, or informallyUSS) is a base element ofz/OS.[2] z/OS UNIX is a certifiedUNIXoperating system implementation (XPG4 UNIX 95) optimized for mainframe architecture. It is the firstUNIX 95 to not be derived from theAT&T source code. Through integration with the rest of z/OS, additionalTime Sharing Option (TSO) commands are available alongside the usual UNIX services, making it possible to process UNIX files usingISPF. Extensions inJCL make it possible to use these files inbatch processing.
UNIX System Services allows UNIX applications from other platforms to run onIBM System z mainframes running z/OS. In many cases only a recompile is necessary, although additional effort may be advisable for z/OS integration (such asSMP/E installation support). While z/OS UNIX supports ASCII andUnicode, and there's no technical requirement to modify ASCII and Unicode UNIX applications, many z/OS users often preferEBCDIC support in their applications including those running in z/OS UNIX. Consequently, z/OS UNIX provides application and administrator services for converting to/from EBCDIC. Programs running under z/OS UNIX have full, secure access to the other internal functions of z/OS. Database access (Db2 via Call Attach) is one example of how z/OS UNIX can access services found elsewhere in z/OS. Naturally such programs cannot be ported to non-mainframe platforms without rewriting if they use these z/OS-specific services. Conversely, if a program adheres to UNIX standards such as POSIX andANSI C, it will be easier to move it between different UNIX operating systems including z/OS UNIX.
The file systems for z/OS UNIX (the olderHFS[3][4] with DFSMS/MVS Version 1 Release 2[5] and the now preferredzFS), which support UNIX-stylelong filenames, appear asdatasets[a] to the rest of z/OS. Numerous core z/OS subsystems and applications rely on UNIX System Services, including the z/OS Management Facility, XML parsing and generation services,OpenSSH, the IBM HTTP Server for z/OS, the z/OS SDK forJava, and some z/OS PKI services as examples. z/OS UNIX also provides ashell environment, OMVS.
z/OS UNIX's predecessor was an operating system component calledOpenEdition MVS, first implemented inMVS/ESA SP 4.3 and enhanced inMVS/ESA 5.1. OpenEdition MVS initially only supported thePOSIX standards, but X/OPEN, the predecessor to The Open Group, certified MVS/ESA SP V5.1.
IBM continues to enhance UNIX System Services. Typically every release of z/OS includes enhancements to z/OS UNIX.
Name changed from OpenEdition to OS/390 UNIX System Services
