- UNIX System Services
UNIX System Services (USS) is a required, included component of
z/OS . USS is a certified UNIX 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 in JCL make it possible to use these files inbatch processing .UNIX System Services allows UNIX applications from other platforms to run on
IBM mainframe s. In many cases only a recompile is necessary, although additional effort may be advisable forz/OS integration (such asSMP/E installation support). Binary programs usinghardcoded ASCII numerical values may need adjustment —z/OS users often prefer or requireEBCDIC support. Programs running under USS have full, secure access to the internal functions of z/OS. Database access (DB2 via Call Attach) is one example of how USS can access services found elsewhere inz/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 standards such as POSIX andANSI C , it will be easier to port to the USS environment.The file systems for USS (the older
HFS and the now preferredzFS ), which support UNIX-stylelong filename s, appear as special datasets to the rest ofz/OS . Numerous core System z subsystems and applications rely on UNIX System Services, including Java.USS also provides a shell environment, OMVS.
USS's predecessor was an operating system component called "OpenEdition MVS", first implemented in
MVS/ESA 4.3 and enhanced inMVS/ESA 5.1. OpenEdition MVS only supported thePOSIX standards. IBM continues to enhance UNIX System Services. In 2007, IBM [http://www.ibm.com/common/ssi/rep_ca/8/897/ENUS207-018/ENUS207018.PDF announced z/OS 1.9] which includes several new USS features, including partial alignment with the newerSingle UNIX Specification Version 3 (UNIX 03).See also
*
Linux on System z
*OpenSolaris for System z
*UTS (Mainframe UNIX) External links
* [http://www-03.ibm.com/servers/eserver/zseries/zos/unix/ UNIX System Services]
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