UNIX System Services

<h2 id="overview">Overview</h2>
<p>UNIX System Services allows UNIX applications from other platforms to run on <a href="/facts/IBM_System_z/JJX9eAsD">IBM System z</a> mainframes running z/OS. In many cases only a recompile is necessary, although additional effort may be advisable for z/OS integration (such as <a href="/facts/SMP%2fE/awfjnzIa">SMP/E</a> installation support). While z/OS UNIX supports ASCII and <a href="/facts/Unicode/DDu3MfPV">Unicode</a>, and there's no technical requirement to modify ASCII and Unicode UNIX applications, many z/OS users often prefer <a href="/facts/EBCDIC/qAhmvgj0">EBCDIC</a> 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 (<a href="/facts/IBM_Db2/2cYITuuY">Db2</a> 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 and <a href="/facts/ANSI_C/rPKeEuPm">ANSI C</a>, it will be easier to move it between different UNIX operating systems including z/OS UNIX.
</p><p>The file systems for z/OS UNIX (the older <a href="/facts/Hierarchical_File_System_(IBM_MVS)/yIGQtAMR">HFS</a><a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a><a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> with DFSMS/MVS Version 1 Release 2<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> and the now preferred <a href="/facts/ZFS_(z%2fOS_file_system)/qft9s1ub">zFS</a>), which support UNIX-style <a href="/facts/Long_filename/HCgRr2aF">long filenames</a>, appear as <a href="/facts/Data_set_(IBM_mainframe)/ker4c5te">datasets</a><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></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, <a href="/facts/OpenSSH/2qxJ3Fe7">OpenSSH</a>, the IBM HTTP Server for z/OS, the z/OS SDK for <a href="/facts/Java_(programming_language)/9ScgFyAL">Java</a>, and some z/OS PKI services as examples.  z/OS UNIX also provides a <a href="/facts/Shell_(computing)/Sa67elS7">shell</a> environment, OMVS.
</p><p>z/OS UNIX's predecessor was an operating system component called <a href="/facts/MVS/VPSmB9ML">OpenEdition MVS</a>, first implemented in <a href="/facts/MVS%2fESA/VPSmB9ML">MVS/ESA</a> SP 4.3 and enhanced in <a href="/facts/MVS%2fESA/VPSmB9ML">MVS/ESA</a> 5.1. OpenEdition MVS initially only supported the <a href="/facts/POSIX/mQkSt234">POSIX</a> standards, but X/OPEN, the predecessor to The Open Group, certified MVS/ESA SP V5.1.
</p><p>IBM continues to enhance UNIX System Services. Typically every release of z/OS includes enhancements to z/OS UNIX.
</p>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Linux_on_IBM_Z/bgLdzJQf">Linux on IBM Z</a></li>
<li><a href="/facts/OpenSolaris_for_System_z/esxL84Yh">OpenSolaris for System z</a></li>
<li><a href="/facts/UTS_(Mainframe_UNIX)/mYJUvLf7">UTS (Mainframe UNIX)</a></li></ul>
<h2 id="notes">Notes</h2>

<h2 id="external-links">External links</h2>
<ul><li><a href="https://ibm.com/servers/eserver/zseries/zos/unix/">UNIX System Services</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>"z/OS base elements". ibm.com. <a href="https://www.ibm.com/docs/en/zos/2.5.0?topic=features-zos-base-elements" target="_blank">https://www.ibm.com/docs/en/zos/2.5.0?topic=features-zos-base-elements</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>"Hierarchical File System" (PDF). ti-leipzig.de. Archived from the original (PDF) on 2004-09-06. Retrieved 2016-05-12. <a href="https://web.archive.org/web/20040906071912/http://www.ti-leipzig.de/os390/book/openmvs/hfs.pdf" target="_blank">https://web.archive.org/web/20040906071912/http://www.ti-leipzig.de/os390/book/openmvs/hfs.pdf</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>"Hierarchical File System Usage Guide" (PDF). IBM. September 2000. Retrieved 2023-04-23. <a href="http://www.redbooks.ibm.com/redbooks/pdfs/sg245482.pdf" target="_blank">http://www.redbooks.ibm.com/redbooks/pdfs/sg245482.pdf</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>"IBM DFSMS/MVS Version 1 Release 2". IBM (Announcement Letter). March 1, 1994. LTR ZP94-0202. <a href="https://www.ibm.com/common/ssi/ShowDoc.wss?docURL=/common/ssi/rep_ca/2/877/ENUSZP94-0202/index.html&request_locale=en" target="_blank">https://www.ibm.com/common/ssi/ShowDoc.wss?docURL=/common/ssi/rep_ca/2/877/ENUSZP94-0202/index.html&request_locale=en</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>HFS has a special dataset type; zFS uses a VSAM Linear Data Set as a container <a href="/wiki/VSAM" target="_blank">/wiki/VSAM</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
</ol>

UNIX System Services open-in-new

UNIX System Services