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VM (Operating system)

z/VM
VM mascot - teddy bear.png
Developer IBM
OS family VM family
Working state Current
Source model 1972–1986 Open source, 1986–present Closed source
Initial release 1972; 45 years ago (1972)
Latest release IBM z/VM V6.3 / July 23, 2013; 3 years ago (2013-07-23)
Platforms System/370, System/390, zSeries, IBM zEnterprise System
License 1962–1976 Public domain, 1976–present Proprietary
Official website www.vm.ibm.com

VM (often: VM/CMS) is 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. This was a System/370 reimplementation of earlier CP/CMS operating system. Milestone versions included VM/SP. The current version, z/VM, is still widely used as one of the main full virtualization solutions for the mainframe market.

The heart of the VM architecture is a control program or hypervisor called VM-CP (usually: CP; sometimes, ambiguously: VM). It runs on the physical hardware, and creates the virtual machine environment. VM-CP provides full virtualization of the physical machine – including all I/O and other privileged operations. It performs the system's resource-sharing, including device management, dispatching, virtual storage management, and other traditional operating system tasks. Each VM user is provided with a separate virtual machine having its own address space, virtual devices, etc., and which is capable of running any software that could be run on a stand-alone machine. A given VM mainframe typically runs hundreds or thousands of virtual machine instances. VM-CP began life as CP-370, a reimplementation of CP-67, itself a reimplementation of CP-40.


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