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VM (operating system)
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VM (operating system)
VM, often written VM/CMS, is a family of virtual machine operating systems used on IBM mainframes including the System/370, System/390, IBM Z and compatible systems. It replaced the older CP-67 that formed the basis of the CP/CMS operating system. It was first released as the free Virtual Machine Facility/370 for the S/370 in 1972, followed by chargeable upgrades and versions that added support for new hardware.
VM creates virtual machines into which a conventional operating system may be loaded to allow user programs to run. Originally, that operating system was CMS, a simple single-user system similar to DOS. VM can also be used with a number of other IBM operating systems, including large systems like MVS or VSE, which are often run on their own without VM. In other cases, VM is used with a more specialized operating system or even programs that provided many OS features. These include RSCS and MUMPS, among others.
The heart of the VM architecture is the Control Program or hypervisor abbreviated CP, VM-CP and 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 ("bare-metal") 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.
Running within each virtual machine is another operating system, a guest operating system. This might be:
The following versions are known:
The CMS in the name refers to the Conversational Monitor System, a component of the product that is a single-user operating system that runs in a virtual machine and provides conversational time-sharing in VM.
IBM coined the term hypervisor for the 360/65 and later used it for the DIAG handler of CP-67.
The Diagnose instruction ('83'x—no mnemonic) is a privileged instruction originally intended by IBM to perform "built-in diagnostic functions, or other model-dependent functions." IBM repurposed DIAG for "communication between a virtual machine and CP." The instruction contains two four-bit register numbers, called Rx and Ry, which can "contain operand storage addresses or return codes passed to the DIAGNOSE interface," and a two-byte code "that CP uses to determine what DIAGNOSE function to perform." The available diagnose functions include:
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VM (operating system)
VM, often written VM/CMS, is a family of virtual machine operating systems used on IBM mainframes including the System/370, System/390, IBM Z and compatible systems. It replaced the older CP-67 that formed the basis of the CP/CMS operating system. It was first released as the free Virtual Machine Facility/370 for the S/370 in 1972, followed by chargeable upgrades and versions that added support for new hardware.
VM creates virtual machines into which a conventional operating system may be loaded to allow user programs to run. Originally, that operating system was CMS, a simple single-user system similar to DOS. VM can also be used with a number of other IBM operating systems, including large systems like MVS or VSE, which are often run on their own without VM. In other cases, VM is used with a more specialized operating system or even programs that provided many OS features. These include RSCS and MUMPS, among others.
The heart of the VM architecture is the Control Program or hypervisor abbreviated CP, VM-CP and 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 ("bare-metal") 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.
Running within each virtual machine is another operating system, a guest operating system. This might be:
The following versions are known:
The CMS in the name refers to the Conversational Monitor System, a component of the product that is a single-user operating system that runs in a virtual machine and provides conversational time-sharing in VM.
IBM coined the term hypervisor for the 360/65 and later used it for the DIAG handler of CP-67.
The Diagnose instruction ('83'x—no mnemonic) is a privileged instruction originally intended by IBM to perform "built-in diagnostic functions, or other model-dependent functions." IBM repurposed DIAG for "communication between a virtual machine and CP." The instruction contains two four-bit register numbers, called Rx and Ry, which can "contain operand storage addresses or return codes passed to the DIAGNOSE interface," and a two-byte code "that CP uses to determine what DIAGNOSE function to perform." The available diagnose functions include:
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