Group Control System(VM)
Encyclopedia
Group Control System 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.
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:
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:
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
made by IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
, meant to run as a guest of VM
VM (operating system)
VM refers to a family of IBM virtual machine operating systems used on IBM mainframes System/370, System/390, zSeries, System z and compatible systems, including the Hercules emulator for personal computers. The first version, released in 1972, was VM/370, or officially Virtual Machine Facility/370...
. GCS is an integral component of the discontinued VM/SP (since VM/SP 4), VM/XA SP, VM/ESA and current z/VM
Z/VM
z/VM is the current version in IBM's VM family of virtual machine operating systems. z/VM was first released in October 2000 and remains in active use and development . It is directly based on technology and concepts dating back to the 1960s, with IBM's CP/CMS on the IBM System/360-67...
IBM System product offerings.
GCS's purpose is to provide an environment to run some specific OS/MVS
MVS
Multiple Virtual Storage, more commonly called MVS, was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers...
-based applications and networking middleware
Middleware
Middleware is computer software that connects software components or people and their applications. The software consists of a set of services that allows multiple processes running on one or more machines to interact...
under VM. To this end, GCS provides a limited simulation of the OS/MVS APIs. While CMS
Conversational Monitor System
The Conversational Monitor System is a relatively simple interactive computing single-user operating system.* CMS is part of IBM's VM family, which runs on IBM mainframe computers...
, the usual VM guest, already has OS simulation, it is not extensive enough to run some applications such as VTAM
VTAM
Virtual Telecommunications Access Method is IBM's software package that provides communications via telecommunication devices for mainframe environments. It is the implementation of Systems Network Architecture for mainframes...
.
Specifically, GCS provides OS multitasking
Computer multitasking
In computing, multitasking is a method where multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is actively executing instructions for...
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
- IUCVIUCVIUCV is a data transfer mechanism in IBM VM line of operating systems.IUCV allows establishing point to point communication channels, either between 2 virtual machines or between a virtual machine and hypervisor services...
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
- RSCSRSCSRSCS,the fundamental software that powered the world’s largest network prior to the Internet and which directly influenced both internet development and user acceptance of networking between independently managed organizations, was an acronym for the Remote Spooling Communications Subsystem...
: 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