VM (operating system)
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| Developer | IBM |
|---|---|
| OS family | VM family |
| Working state | Current |
| Source model | 1972–1986 Open source, 1986–present Closed source |
| Initial release | 1972 |
| Latest release | IBM z/VM V6.3 / July 23, 2013 |
| Platforms | System/370, System/390, zSeries, IBM zEnterprise System |
| License | 1962–1976 Public domain, 1976–present Proprietary |
| Official website | www |
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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