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</style><table class="infobox vevent"><tbody><tr><th colspan="2" class="infobox-above" style="background-color: #e0e0e0;">Group Control System (GCS)</th></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="Programmer" title="Programmer">Developer</a></th><td class="infobox-data"><a href="IBM" title="IBM">IBM</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Marketing target</th><td class="infobox-data"><a href="IBM_mainframes" class="mw-redirect" title="IBM mainframes">IBM mainframe computers</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="Software_license" title="Software license">License</a></th><td class="infobox-data"><a href="Proprietary_software" title="Proprietary software">Proprietary</a></td></tr></tbody></table>
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</style><table class="sidebar sidebar-collapse nomobile"><tbody><tr><th class="sidebar-title"><a href="History_of_IBM_mainframe_operating_systems" title="History of IBM mainframe operating systems">History of IBM mainframe operating systems</a></th></tr><tr><td class="sidebar-content">
<div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)">Early mainframe computer OSes</div><div class="sidebar-list-content mw-collapsible-content" style="text-align: left">
<ul><li><a href="GM-NAA_I/O" title="GM-NAA I/O">GM OS & GM-NAA I/O</a> (1955)</li>
<li><a href="BESYS" title="BESYS">BESYS</a> (1957)</li>
<li><a href="University_of_Michigan_Executive_System" title="University of Michigan Executive System">UMES</a> (1958)</li>
<li><a href="SHARE_Operating_System" title="SHARE Operating System">SOS</a> (1959)</li>
<li><a href="IBM_7090/94_IBSYS" title="IBM 7090/94 IBSYS">IBSYS</a> (1960)</li>
<li><a href="Compatible_Time-Sharing_System" title="Compatible Time-Sharing System">MIT CTSS</a> (1961)</li>
<li>7040/7044 Operating System (16/32K) (7040-PR-150)</li>
<li>1410/7010 Operating System<br>(1410-PR-155)</li></ul></div></div></td>
</tr><tr><td class="sidebar-content">
<div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)">Miscellaneous S/360 line OSes</div><div class="sidebar-list-content mw-collapsible-content" style="text-align: left">
<ul><li><a href="BOS/360" title="BOS/360">BOS/360</a> (1965)</li>
<li><a href="DOS/360_and_successors#TOS/360" title="DOS/360 and successors">TOS/360</a> (1965)</li>
<li><a href="TSS_(operating_system)" title="TSS (operating system)">TSS/360</a> (1967)</li>
<li><a href="Michigan_Terminal_System" title="Michigan Terminal System">MTS</a> (1967)</li>
<li><a href="ORVYL_and_WYLBUR" title="ORVYL and WYLBUR">ORVYL</a> (1967)</li>
<li>RACS (1965)
<ul><li><a href="IBM_Remote_Access_Computing" title="IBM Remote Access Computing">RAX</a> (1966)
<ul><li><a href="MUSIC/SP" title="MUSIC/SP">MUSIC</a> (1972)
<ul><li><a href="MUSIC/SP" title="MUSIC/SP">MUSIC/SP</a> (1985)</li></ul></li></ul></li></ul></li></ul></div></div></td>
</tr><tr><td class="sidebar-content">
<div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)"><a href="DOS/360_and_successors" title="DOS/360 and successors">DOS/360 and successors</a> (1966)</div><div class="sidebar-list-content mw-collapsible-content" style="text-align: left">
<ul><li><a href="DOS/360_and_successors#DOS/360" title="DOS/360 and successors">DOS/360</a> (1965)</li>
<li><a href="DOS/VS" class="mw-redirect" title="DOS/VS">DOS/VS</a> (1972)</li>
<li><a href="DOS/VSE" class="mw-redirect" title="DOS/VSE">DOS/VSE</a> (1979)
<ul><li>VSE/AF (1979)</li></ul></li>
<li><a href="VSE/SP" class="mw-redirect" title="VSE/SP">VSE/SP</a> (1983, 1985)</li>
<li><a href="VSE/ESA" class="mw-redirect" title="VSE/ESA">VSE/ESA</a> (1991)</li>
<li><a href="VSE_(operating_system)" title="VSE (operating system)">z/VSE</a> (2005)</li>
<li><a href="VSE_(operating_system)" title="VSE (operating system)">VSE<sup>n</sup></a> (2021)</li></ul></div></div></td>
</tr><tr><td class="sidebar-content">
<div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)"><a href="OS/360_and_successors" title="OS/360 and successors">OS/360 and successors</a> (1966)</div><div class="sidebar-list-content mw-collapsible-content" style="text-align: left">
<ul><li><a href="MFT_(operating_system)" class="mw-redirect" title="MFT (operating system)">MFT</a> (1966)</li>
<li><a href="MFT_II" class="mw-redirect" title="MFT II">MFT II</a> (1968)
<ul><li><a href="OS/VS1" title="OS/VS1">OS/VS1</a> (1972)</li>
<li><a href="OS/VS1_BPE" class="mw-redirect" title="OS/VS1 BPE">OS/VS1 BPE</a></li></ul></li>
<li><a href="Multiprogramming_with_a_Variable_number_of_Tasks" class="mw-redirect" title="Multiprogramming with a Variable number of Tasks">MVT</a> (1967)
<ul><li><a href="65MP" class="mw-redirect" title="65MP">65MP</a></li>
<li><a href="OS/VS2_(SVS)" title="OS/VS2 (SVS)">OS/VS2R1</a> (SVS) (1972)</li>
<li><a href="MVS" title="MVS">MVS</a> (OS/VS2R2 and later) (1974)
<ul><li>MVS/SE (1978)</li>
<li>MVS/SE 2 (1979)</li>
<li><a href="MVS/SP" class="mw-redirect" title="MVS/SP">MVS/SP</a> Version 1 (1980)</li>
<li><a href="MVS/XA" class="mw-redirect" title="MVS/XA">MVS/XA</a> (1983)</li>
<li><a href="MVS/ESA" class="mw-redirect" title="MVS/ESA">MVS/ESA</a> (1988)</li>
<li><a href="OS/390" title="OS/390">OS/390</a> (1995)</li>
<li><a href="Z/OS" title="Z/OS">z/OS</a> (2000)</li></ul></li></ul></li></ul></div></div></td>
</tr><tr><td class="sidebar-content">
<div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)"><a href="History_of_CP/CMS" title="History of CP/CMS">VM line</a></div><div class="sidebar-list-content mw-collapsible-content" style="text-align: left">
<ul><li><a href="IBM_CP-40" title="IBM CP-40">CP-40</a><a href="CP/CMS" title="CP/CMS">/CMS</a> (1967)</li>
<li><a href="CP-67" title="CP-67">CP-67</a><a href="CP/CMS" title="CP/CMS">/CMS</a> (1967)</li>
<li><a href="VP/CSS" title="VP/CSS">VP/CSS</a> (1968)</li>
<li><a href="VM_(operating_system)" title="VM (operating system)">VM/370</a> (1972)</li>
<li>VM/BSE (BSEPP)</li>
<li>VM/SE (SEPP)</li>
<li><a href="VM_(operating_system)" title="VM (operating system)">VM/SP</a> (1980)</li>
<li>VM/XA MA (1984)</li>
<li>VM/XA SF (1985)</li>
<li>VM/XA SP (1988)</li>
<li><a href="VM_(operating_system)" title="VM (operating system)">VM/ESA</a> (1990)</li>
<li><a href="Z/VM" title="Z/VM">z/VM</a> (2000)</li></ul></div></div></td>
</tr><tr><td class="sidebar-content">
<div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)">TPF line</div><div class="sidebar-list-content mw-collapsible-content" style="text-align: left">
<ul><li><a href="IBM_Airline_Control_Program" title="IBM Airline Control Program">ACP</a> (1967)</li>
<li><a href="Transaction_Processing_Facility" title="Transaction Processing Facility">TPF</a> (1979)</li>
<li><a href="Z/TPF" class="mw-redirect" title="Z/TPF">z/TPF</a> (2005)</li></ul></div></div></td>
</tr><tr><td class="sidebar-content">
<div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)"><a href="Unix" title="Unix">UNIX</a> and <a href="Unix-like" title="Unix-like">Unix-like</a></div><div class="sidebar-list-content mw-collapsible-content" style="text-align: left">
<ul><li><a href="Amdahl_UTS" title="Amdahl UTS">UTS</a> (1981)</li>
<li><a href="IBM_AIX#IBM_mainframes" title="IBM AIX">AIX/370</a> (1990)</li>
<li><a href="IBM_AIX#IBM_mainframes" title="IBM AIX">AIX/ESA</a> (1991)</li>
<li>MVS/ESA <a href="MVS#MVS.2FESA" title="MVS">OpenEdition</a> (1993)</li>
<li>VM/ESA <a href="VM_(operating_system)#OpenEdition_extensions" title="VM (operating system)">OpenEdition</a> (1995)</li>
<li>OS/390 <a href="UNIX_System_Services" title="UNIX System Services">UNIX System Services</a> (1996)</li>
<li><a href="Linux_on_IBM_Z" title="Linux on IBM Z">Linux</a> (1999)</li>
<li>z/VM <a href="VM_(operating_system)#OpenEdition_extensions" title="VM (operating system)">OpenExtensions</a> (2000)</li>
<li>z/OS <a href="UNIX_System_Services" title="UNIX System Services">UNIX System Services</a> (2001)</li>
<li><a href="OpenSolaris_for_System_z" title="OpenSolaris for System z">OpenSolaris</a> (2008)</li></ul></div></div></td>
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<p><b>Group Control System</b> (<b>GCS</b>) is an <a href="Operating_system" title="Operating system">operating system</a> made by <a href="IBM" title="IBM">IBM</a>, meant to run as a guest of <a href="VM_(operating_system)" title="VM (operating system)">VM</a>.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> GCS is an integral component of the discontinued <a href="VM/SP" class="mw-redirect" title="VM/SP">VM/SP</a> (since VM/SP 4), VM/XA SP, <a href="VM/ESA" class="mw-redirect" title="VM/ESA">VM/ESA</a> and current <a href="Z/VM" title="Z/VM">z/VM</a> IBM System product offerings.
</p>
<div class="mw-heading mw-heading2"><h2 id="Overview">Overview</h2></div>
<p>GCS's purpose is to provide an environment to run some specific <a href="MVS" title="MVS">OS/MVS</a>-based applications and networking <a href="Middleware" title="Middleware">middleware</a> under VM. To this end, GCS provides a limited simulation of the OS/MVS APIs. While <a href="Conversational_Monitor_System" title="Conversational Monitor System">CMS</a>, the usual VM guest, already has OS simulation, it is not extensive enough to run some applications such as <a href="VTAM" class="mw-redirect" title="VTAM">VTAM</a>.
</p><p>Specifically, GCS provides <a href="Computer_multitasking" title="Computer multitasking">OS multitasking</a> support. In order to be able to spread the load over several virtual machines, GCS also implements a notion of group where each group member virtual machine can interact with one another.
</p><p>To implement this, GCS uses several techniques:
</p>
<ul><li>A writable shared segment</li>
<li><a href="IUCV" title="IUCV">IUCV</a> communications between virtual machines</li>
<li>A recovery virtual machine, designed to clean up locks in the shared segments when virtual machines unexpectedly leave the group</li></ul>
<p>GCS is not designed to be a multi-purpose user operating system such as CMS. For example, it does not allow for file editing.
</p><p>Examples of programs designed to run under GCS are:
</p>
<ul><li>VM/VTAM : The VM implementation of the VTAM stack</li>
<li><a href="RSCS" title="RSCS">RSCS</a> : The Remote Spooling Communication Subsystem, which, when associated with an instance of VM/VTAM, can use SNA resources to communicate with other SNA/NJE hosts</li>
<li>NETVIEW : A networking monitoring service</li></ul>
<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
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</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.ibm.com/docs/en/zvm/7.2?topic=overview-what-gcs-is">"What GCS Is"</a>. <i><a href="IBM" title="IBM">IBM</a></i>.</cite></span>
</li>
</ol></div></div>
<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>
<ul><li><a rel="nofollow" class="external text" href="https://archive.today/20121210084740/http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/HCSF5B20/CCONTENTS?SHELF=EZ2ZVM01&DN=SC24-6098-02&DT=20070419173550">z/VM 5.3 Group Control System</a></li></ul>
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</style></div><div role="navigation" class="navbox" aria-labelledby="Operating_systems_by_IBM311" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><div id="Operating_systems_by_IBM311" style="font-size:114%;margin:0 4em"><a href="Operating_system" title="Operating system">Operating systems</a> by <a href="IBM" title="IBM">IBM</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Supercomputer" title="Supercomputer">Supercomputer</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="INK_(operating_system)" title="INK (operating system)">INK</a></li>
<li><a href="CNK_operating_system" title="CNK operating system">CNK</a></li>
<li><a href="Red_Hat_Enterprise_Linux" title="Red Hat Enterprise Linux">Red Hat Enterprise Linux</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Server_(computing)" title="Server (computing)">Server</a>, <a href="Mainframe_computer" title="Mainframe computer">mainframe</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="IBM_7090/94_IBSYS" title="IBM 7090/94 IBSYS">IBSYS</a></li>
<li><a href="BOS/360" title="BOS/360">BOS/360</a></li>
<li><a href="TOS/360" class="mw-redirect" title="TOS/360">TOS/360</a></li>
<li><a href="TSS_(operating_system)" title="TSS (operating system)">TSS/360</a></li>
<li><a href="IBM_Remote_Access_Computing" title="IBM Remote Access Computing">RAX</a></li>
<li><a href="DOS/360_and_successors" title="DOS/360 and successors">DOS/360 and successors</a>
<ul><li><a href="VSE_(operating_system)" title="VSE (operating system)">VSE</a></li></ul></li>
<li><a href="OS/360_and_successors" title="OS/360 and successors">OS/360 and successors</a>
<ul><li><a href="OS/VS1" title="OS/VS1">OS/VS1</a></li>
<li><a href="OS/VS2_(SVS)" title="OS/VS2 (SVS)">SVS</a></li>
<li><a href="MVS" title="MVS">MVS</a></li>
<li><a href="OS/390" title="OS/390">OS/390</a></li>
<li><a href="Z/OS" title="Z/OS">z/OS</a></li></ul></li>
<li><a href="History_of_CP/CMS" title="History of CP/CMS">VM line</a></li>
<li><a href="IBM_Airline_Control_Program" title="IBM Airline Control Program">ACP</a></li>
<li><a href="Transaction_Processing_Facility" title="Transaction Processing Facility">TPF</a></li>
<li><a href="Control_Program_Facility" title="Control Program Facility">CPF</a></li>
<li><a href="Stratus_VOS" title="Stratus VOS">System/88 OS</a></li>
<li><a href="IBM_i" title="IBM i">IBM i</a></li>
<li><a href="IBM_AIX" title="IBM AIX">AIX</a></li>
<li><a href="Linux_on_IBM_Z" title="Linux on IBM Z">zLinux</a></li>
<li><a href="IBM_8100_DPCX" title="IBM 8100 DPCX">DPCX</a></li>
<li><a href="IBM_DPPX" title="IBM DPPX">DPPX</a></li>
<li><a href="System_Support_Program" title="System Support Program">SSP</a></li>
<li><a href="Special_Real_Time_Operating_System" title="Special Real Time Operating System">SRTOS</a></li>
<li><a href="Red_Hat_Enterprise_Linux" title="Red Hat Enterprise Linux">Red Hat Enterprise Linux</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Desktop_computer" title="Desktop computer">Desktop</a>, <a href="Workstation" title="Workstation">workstation</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Textpack" class="mw-redirect" title="Textpack">Textpack</a></li>
<li><a href="IBM_PC_DOS" title="IBM PC DOS">PC DOS</a>
<ul><li><a href="DOS/V" title="DOS/V">DOS/V</a></li></ul></li>
<li><a href="PC/IX" class="mw-redirect" title="PC/IX">PC/IX</a></li>
<li><a href="IBM_AIX" title="IBM AIX">AIX</a></li>
<li><a href="OS/2" title="OS/2">OS/2</a></li>
<li><a href="IBM_RT_PC#Software" title="IBM RT PC">AOS</a></li>
<li><a href="Red_Hat_Enterprise_Linux" title="Red Hat Enterprise Linux">Red Hat Enterprise Linux</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Point_of_sale" title="Point of sale">Point of sale</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="FlexOS#4680_OS" title="FlexOS">4680 OS</a></li>
<li><a href="4690_Operating_System" title="4690 Operating System">4690 OS</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Projects</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Taligent" title="Taligent">Taligent</a></li>
<li><a href="Workplace_OS" title="Workplace OS">Workplace OS</a></li>
<li><a href="Project_Monterey" title="Project Monterey">Monterey</a></li>
<li><a href="Project_Trillian" class="mw-redirect" title="Project Trillian">Trillian</a></li>
<li><a href="K42" title="K42">K42</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Fedora_Linux" title="Fedora Linux">Fedora Linux</a></li></ul>
</div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div><span class="noviewer" typeof="mw:File"><span title="Category"></span></span> Category</div></td></tr></tbody></table></div>
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