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closed source initial release 1972 50 years ago 1972 latest release ibm z vm v7 2 september 16 2020 2 years ago 2020 09 16 marketing target ibm mainframe computers available in english platforms system 370 system 390 zseries ibm zenterprise system license 1972 1981 public domain 1976 present proprietary official website www vm ibm com 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 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 os 390 unix system services 1996 linux 1999 z os unix system services 2001 opensolaris 2008 v t e the default login screen on vm 370 release 6 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 following versions are known virtual machine facility 370 vm 370 released in 1972 is a system 370 reimplementation of earlier cp cms operating system vm 370 basic system extensions program product vm bse bsepp is an enhancement to vm 370 that adds support for more devices such as 3370 type fixed block architecture dasd drives improvements to the cms environment such as an improved editor and some stability enhancements to cp vm 370 system extensions program product vm se sepp is an enhancement to vm 370 that includes the facilities of vm bse as well as a few additional fixes and features virtual machine system product vm sp a milestone version 1 replaces vm 370 vm bse and vm se release 1 added exec2 and xedit system product editor release 3 added rexx release 6 added the shared filesystem virtual machine system product high performance option 2 vm sp hpo adds additional device support and functionality to vm sp and allows certain s 370 machines that can utilize more than 16 mb of real storage to do so up to 64 mb this version was intended for users that would be running multiple s 370 guests at once 3 virtual machine extended architecture migration aid 4 vm xa ma is intended to ease the migration from mvs 370 to mvs xa by allowing both to run concurrently on the same processor complex virtual machine extended architecture system facility 5 vm xa sf is an upgraded vm xa ma with improved functionality and performance virtual machine extended architecture system product 6 vm xa sf is an upgraded vm xa ma with improved functionality and performance offered as a replacement for vm sp hpo on machines supporting s 370 xa it includes a version of cms that can run in either s 370 or s 370 xa mode virtual machine enterprize systems architecture 7 vm esa provides the facilities of vm sp vm sp hpo and vm xa sp vm esa version 1 can run in s 370 esa 370 or esa 390 mode it does not support s 370 xa mode version 2 only runs in esa 390 mode the s 370 capable versions of vm esa were actually their own separate version from the esa 390 versions of vm esa as the s 370 versions are based on the older vm sp hpo codebase and the esa 390 versions are based on the newer vm xa codebase z vm 8 z vm the last version still widely used as one of the main full virtualization solutions for the mainframe market citation needed z vm 4 4 was the last version that could run in esa 390 mode subsequent versions only run in z architecture mode 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 contents 1 overview 2 hypervisor interface 2 1 cms use of diagnose 3 minidisks 4 shared file system 5 history 6 cp commands 7 openedition extensions 8 vm mascot 9 criticism 10 notes 11 see also 12 references 13 external links 13 1 vm sources 13 2 primary cp cms sources 13 3 additional cp cms sources 13 4 background cp cms sources 13 5 additional on line cp cms resources 13 6 other resources overview edit 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 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 cms conversational monitor system renamed from the cambridge monitor system of cp cms most virtual machines run cms a lightweight single user operating system its interactive environment is comparable to that of a single user pc including a file system programming services device access and command line processing while an earlier version of cms was uncharitably described as cp m on a mainframe the comparison is an anachronism the author of cp m gary kildall was an experienced cms user gcs group control system which provides a limited simulation of the mvs api ibm originally provided gcs in order to run vtam without a service os vs1 virtual machine and vtam communications network application vcna rscs v2 also ran under gcs a mainstream operating system ibm s mainstream operating systems i e the mvs dos vse or tss 370 families can be loaded and run without modification the vm hypervisor treats guest operating systems as application programs with exceptional privileges it prevents them from directly using privileged instructions those which would let applications take over the whole system or significant parts of it but simulates privileged instructions on their behalf most mainframe operating systems terminate a normal application which tries to usurp the operating system s privileges the vm hypervisor can simulate several types of console terminals for the guest operating system such as the hardcopy line mode 3215 the graphical 3270 family and the integrated console on newer system 390 and system z machines other users can then access running virtual machines using the dial command at the logon screen which will connect their terminal to the first available emulated 3270 device or the first available 2703 device if the user is dialing from a typewriter terminal another copy of vm a second level instance of vm can be fully virtualized inside a virtual machine this is how vm development and testing is done a second level vm can potentially implement a different virtualization of the hardware this technique was used to develop s 370 software before s 370 hardware was available and it has continued to play a role in new hardware development at ibm the literature cites practical examples of virtualization five levels deep 9 levels of vm below the top are also treated as applications but with exceptional privileges a copy of the mainframe version of aix or linux in the mainframe environment these operating systems often run under vm and are handled like other guest operating systems they can also run as native operating systems on the bare hardware there was also the short lived ix 370 as well as s 370 and s 390 versions of aix aix 370 and aix esa a specialized vm subsystem several non cms systems run within vm cp virtual machines providing services to cms users such as spooling interprocess communications specialized device support and networking they operate behind the scenes extending the services available to cms without adding to the vm cp control program by running in separate virtual machines they receive the same security and reliability protections as other vm users examples include rscs remote spooling and communication subsystem aka vnet communication and information transfer facilities between virtual machines and other systems 10 racf resource access control facility a security system shared file system sfs which organizes shared files in a directory tree the servers are commonly named vmservx vtam virtual telecommunications access method a facility that provides support for a systems network architecture network pvm vm pass through facility a facility that provides remote access to other vm systems tcpip smtp ftpserve portmap vmnfs a set of service machines that provide tcp ip networking to vm cms db2 server for vm a sql database system the servers are often named similarly to sqlmach and sqlmstr dirmaint a simplified user directory management system the directory is a listing of every account on the system including virtual hardware configuration user passwords and minidisks mumps vm an implementation of the mumps database and programming language which could run as guest on vm 370 11 mumps vm was introduced in 1987 and discontinued in 1991 12 a user written or modified operating system such as national css s css or boston university s vps vm hypervisor interface edit ibm coined the term hypervisor for the 360 65 13 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 14 ibm repurposed diag for communication between a virtual machine and cp 15 16 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 15 a few of the available diagnose functions are listed below hexadecimal code function 0000 store extended identification code 0004 examine real storage 0008 virtual console function execute a cp command 0018 standard dasd i o 0020 general i o execute any valid ccw chain on a tape or disk device 003c update the vm 370 directory 0058 3270 virtual console interface perform full screen i o on an ibm 3270 terminal 0060 determine virtual machine storage size 0068 virtual machine communication facility vmcf cms use of diagnose edit at one time cms was capable of running on a bare machine as a true operating system though such a configuration would be unusual it now runs only as a guest os under vm this is because cms relies on a hypervisor interface to vm cp to perform file system operations and request other vm services this paravirtualization interface provides a fast path to vm cp to avoid the overhead of full simulation was first developed as a performance improvement for cp cms release 2 1 an important early milestone in cp s efficiency uses a non virtualized model dependent machine instruction as a signal between cms and cp diag diagnose minidisks edit cms starting up after the user maint system administrator has logged in cms and other operating systems often have dasd requirements much smaller than the sizes of actual volumes for this reason cp allows an installation to define virtual disks of any size up to the capacity of the device for ckd volumes a minidisk must be defined in full cylinders a minidisk has the same attributes as the underlying real disk except that it is usually smaller and the beginning of each minidisk is mapped to cylinder or block 0 the minidisk may be a accessed using the same channel programs as the real disk a minidisk that has been initialized with a cms file system is referred to as a cms minidisk although cms is not the only system that can use them it is common practice to define full volume minidisks for use by such guest operating systems as z os instead of using dedicate to assign the volume to a specific virtual machine in addition full pack links are often defined for every dasd on the system and are owned by the maint userid these are used for backing up the system using the dasd dump restore program where the entire contents of a dasd are written to tape or another dasd exactly the cms editor on vm 370 editing a cobol program source file shared file system edit vm sp release 6 introduced the shared file system 17 which vastly improved cms file storage capabilities the cms minidisk file system does not support directories folders at all however the sfs does sfs also introduces more granular security with cms minidisks the system can be configured to allow or deny users read only or read write access to a disk but single files cannot have the same security sfs alleviates this and vastly improves performance the sfs is provided by service virtual machines on a modern vm system there are usually three that are required vmservr the recovery machine that does not actually serve any files vmservs the server for the vmsys filepool and vmservu the server for the vmsysu user filepool 18 the file pool server machines own several minidisks usually including a cms a disk virtual device address 191 containing the file pool configuration files a control disk a log disk and any number of data disks that actually store user files invoking the system 360 cobol compiler on vm 370 cms then loading and running the program with modern vm versions most of the system can be installed to sfs with the few remaining minidisks being the ones absolutely necessary for the system to start up and the ones being owned by the filepool server machines an example of a non cms guest operating system running under vm 370 dos vs release 34 the dos vs system is now prompting the operator to enter a supervisor name to continue loading if a user account is configured to only use sfs and does not own any minidisks the user s a disk will be filepool userid and any subsequent directories that the user creates will be filepool userid dir1 dir2 dir3 where the equivalent unix file path is dir1 dir2 dir3 sfs directories can have much more granular access controls when compared to minidisks which as mentioned above can often only have a read password a write password and a multi write passwor...