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IBM operating system

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Operating system

Group Control System (GCS)
Developer	IBM
Marketing target	IBM mainframe computers
License	Proprietary

History of IBM mainframe operating systems
Early mainframe computer OSes GM OS & GM-NAA I/O (1955) BESYS (1957) UMES (1958) SOS (1959) IBSYS (1960) MIT CTSS (1961) 7040/7044 Operating System (16/32K) (7040-PR-150) 1410/7010 Operating System (1410-PR-155)
Miscellaneous S/360 line OSes BOS/360 (1965) TOS/360 (1965) TSS/360 (1967) MTS (1967) ORVYL (1967) RACS (1965) RAX (1966) MUSIC (1972) MUSIC/SP (1985)
DOS/360 and successors (1966) DOS/360 (1965) DOS/VS (1972) DOS/VSE (1979) VSE/AF (1979) VSE/SP (1983, 1985) VSE/ESA (1991) z/VSE (2005) VSE (2021)
OS/360 and successors (1966) MFT (1966) MFT II (1968) OS/VS1 (1972) OS/VS1 BPE MVT (1967) 65MP OS/VS2R1 (SVS) (1972) MVS (OS/VS2R2 and later) (1974) MVS/SE (1978) MVS/SE 2 (1979) MVS/SP Version 1 (1980) MVS/XA (1983) MVS/ESA (1988) OS/390 (1995) z/OS (2000)
VM line CP-40 /CMS (1967) CP-67 /CMS (1967) VP/CSS (1968) VM/370 (1972) VM/BSE (BSEPP) VM/SE (SEPP) VM/SP (1980) VM/XA MA (1984) VM/XA SF (1985) VM/XA SP (1988) VM/ESA (1990) z/VM (2000)
TPF line ACP (1967) TPF (1979) z/TPF (2005)
UNIX and Unix-like UTS (1981) AIX/370 (1990) AIX/ESA (1991) MVS/ESA OpenEdition (1993) VM/ESA OpenEdition (1995) OS/390 UNIX System Services (1996) Linux (1999) z/VM OpenExtensions (2000) z/OS UNIX System Services (2001) OpenSolaris (2008)
v t e

Group Control System (GCS) is an operating system made by IBM, meant to run as a guest of VM. GCS is an integral component of the discontinued VM/SP (since VM/SP 4), VM/XA SP, VM/ESA and current z/VM IBM System product offerings.

Overview

GCS's purpose is to provide an environment to run some specific OS/MVS-based applications and networking middleware under VM. To this end, GCS provides a limited simulation of the OS/MVS APIs. While CMS, the usual VM guest, already has OS simulation, it is not extensive enough to run some applications such as VTAM.

Specifically, GCS provides OS multitasking 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.

To implement this, GCS uses several techniques:

A writable shared segment
IUCV communications between virtual machines
A recovery virtual machine, designed to clean up locks in the shared segments when virtual machines unexpectedly leave the group

GCS is not designed to be a multi-purpose user operating system such as CMS. For example, it does not allow for file editing.

Examples of programs designed to run under GCS are:

VM/VTAM : The VM implementation of the VTAM stack
RSCS : 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
NETVIEW : A networking monitoring service

References

"What GCS Is". IBM.

External links

z/VM 5.3 Group Control System

v t e Operating systems by IBM
Supercomputer	INK CNK Red Hat Enterprise Linux
Server, mainframe	IBSYS BOS/360 TOS/360 TSS/360 RAX DOS/360 and successors VSE OS/360 and successors OS/VS1 SVS MVS OS/390 z/OS VM line ACP TPF CPF System/88 OS IBM i AIX zLinux DPCX DPPX SSP SRTOS Red Hat Enterprise Linux
Desktop, workstation	Textpack PC DOS DOS/V PC/IX AIX OS/2 AOS Red Hat Enterprise Linux
Point of sale	4680 OS 4690 OS
Projects	Taligent Workplace OS Monterey Trillian K42
Related	Fedora Linux
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