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49-853: VNET was first deployed as a private host to host network among CP/67 and VM/370 mainframes beginning before 1975. It was based on RSCS , a virtual machine –based communications program and an inter machine protocol developed in IBM's Advanced Systems Development Division's Remote Service System (RSS) prototype which produced some of the technology in the IBM Tivoli product. RSCS used the Binary Synchronous Communications (BSC) protocol, not SNA/SDLC, to support file to file transfer among virtual machine users. The first several nodes included Scientific Centers and Poughkeepsie, New York lab sites. RSCS-compatible communications code

98-634: A Token Ring or Ethernet network). The stack provided support for Telnet connections, from either simple line-mode terminal emulators or VT100-compatible emulators, or proper IBM 3270 terminal emulators. The stack also provided an FTP server. IBM also produced an optional NFS server for VM; early versions were rather primitive, but modern versions are much more advanced. There was also a fourth networking option, known as VM/Pass-Through Facility (or more commonly called, PVM). PVM, like VTAM, allowed for connections to remote VM/CMS systems, as well as other IBM systems. If two VM/CMS nodes were linked together over

147-488: A 19.2 kbit/s trans-Atlantic satellite circuit in late 1977 was considered a major step forward. End users typically sent files between 100 and 100,000 bytes in length. The user could expect delivery within one minute to several hours. File delivery was acknowledged on a hop by hop basis but there was no end to end delivery confirmation. However, by the late 1970s an email application was developed that provided delivery confirmation as well as message archiving. What began as

196-542: A channel-to-channel link or bisync link (possibly using a dialup modem or leased line), a user could remotely connect to either system by entering "DIAL PVM" on the VM login screen, then entering the system node name (or choosing it from a list of available nodes). Alternatively, a user running CMS could use the PASSTHRU program that was installed alongside PVM, allowing for quick access to remote systems without having to log out of

245-533: 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

294-436: 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: 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

343-492: A dialog to create an email, from which the user could send it. If the user specified an address in the form of user at node , the email file would be delivered to RSCS, which would then deliver it to the target user on the target system. If the site has TCP/IP installed, RSCS could work with the SMTP service machine to deliver notes (emails) to remote systems, as well as receive them. If the user specified user at some.host.name ,

392-402: A given application, in most of the cases, a bare-metal implementation will run faster, using less memory and so being more power efficient. This is because operating systems, as any program, need some execution time and memory space to run, and these are no longer needed on bare-metal. For instance, any hardware feature that includes inputs and outputs are directly accessible on bare-metal, whereas

441-544: A read password, a write password, and a multi-write password). SFS directories also solve the issues that may arise when two users write to the same CMS minidisk at the same time, which may cause disk corruption (as the CMS VM performing the writes may be unaware that another CMS instance is also writing to the minidisk). The file pool server machines also serve a closely related filesystem: the Byte File System. BFS

490-464: A research activity among engineers and scientists became, by 1980, a valuable business asset for many organizations within IBM. The first widely disruptive computer worm , " Christmas Tree EXEC " in December 1987, originated on BITNET and spread to this network. This computer networking article is a stub . You can help Misplaced Pages by expanding it . VM/370 VM (often: VM/CMS )

539-464: A shell can then be started with OPENVM SHELL . Unlike the normal SFS, access to BFS filesystems is controlled by POSIX permissions (with chmod and chown ). Starting with z/VM Version 3, IBM integrated OpenEdition into z/VM and renamed it OpenExtensions. OpenEdition and OpenExtensions provide POSIX.2 compliance to CMS. Programs compiled to run under the OpenExtensions shell are stored in

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588-521: A single system. z/VM was first released in October 2000 and remains in active use and development. IBM and third parties have offered many applications and tools that run under VM. Examples include RAMIS , FOCUS , SPSS , NOMAD , DB2 , REXX , RACF , and OfficeVision . Current VM offerings run the gamut of mainframe applications, including HTTP servers, database managers, analysis tools, engineering packages, and financial systems. As of release 6,

637-471: A single user (or virtual machine) could not use more than 16 MB. The functions of the spool filesystem were also improved, allowing 9900 spool files to be created per user, rather than 9900 for the whole system. The architecture of the spool filesystem was also enhanced, each spool file now had a unique user ID associated with it, and reader file control blocks were now held in virtual storage. The system could also be configured to deny certain users access to

686-506: 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: The following versions are known: The CMS in the name refers to the Conversational Monitor System,

735-416: 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

784-762: A very substantial portion of the mid-range machines that were built in Endicott. Before fifteen years had passed, there would be more VM licenses than MVS licenses. A PC DOS version that runs CMS on the XT/370 (and later on the AT/370) is called VM/PC. VM/PC 1.1 was based on VM/SP release 3. When IBM introduced the P/370 and P/390 processor cards, a PC could now run full VM systems, including VM/370, VM/SP, VM/XA, and VM/ESA (these cards were fully compatible with S/370 and S/390 mainframes, and could run any S/370 operating system from

833-483: 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: At one time, CMS was capable of running on a bare machine , as a true operating system (though such

882-585: 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 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

931-475: Is generally done using a close-to-hardware language, such as Rust , C++ , C , assembly language , or even for small amounts of code or very new processors machine code directly. All the previous issues inevitably mean that bare-metal programs are very rarely portable . Early computers, such as the PDP-11 , allowed programmers to load a program, supplied in machine code , to RAM . The resulting operation of

980-561: Is provided by either C/370 or C for VM/ESA. Neither the CMS filesystem nor the standard VM Shared File System has any support for UNIX-style files and paths; instead, the Byte File System is used. Once a BFS extent is created in an SFS file pool, the user can mount it using the OPENVM MOUNT /../VMBFS:fileservername:filepoolname /path/to/mount/point . The user must also mount the root filesystem, done with OPENVM MOUNT /../VMBFS:VMSYS:ROOT/ / ,

1029-472: 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

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1078-700: Is used to store files on a UNIX-style filesystem. Its primary use is for the VM OpenExtensions POSIX environment for CMS. The CMS user virtual machines themselves communicate with the SFS server virtual machines through the IUCV mechanism. The early history of VM is described in the articles CP/CMS and History of CP/CMS . VM/370 is a reimplementation of CP/CMS, and was made available in 1972 as part of IBM's System/370 Advanced Function announcement (which added virtual memory hardware and operating systems to

1127-464: The System/370 series). Early releases of VM through VM/370 Release 6 continued in open source through 1981, and today are considered to be in the public domain . This policy ended in 1977 with the chargeable VM/SE and VM/BSE upgrades and in 1980 with VM/System Product (VM/SP). However, IBM continued providing updates in source form for existing code for many years, although the upgrades to all but

1176-522: 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. 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. If

1225-419: The 31-bit era, e.g., MVS/ESA, VSE/ESA). In addition to the base VM/SP releases, IBM also introduced VM/SP HPO (High Performance Option). This add-on (which is installed over the base VM/SP release) improved several key system facilities, including allowing the usage of more than 16 MB of storage (RAM) on supported models (such as the IBM 4381). With VM/SP HPO installed, the new limit was 64 MB; however,

1274-585: The MVS Performance Group in the early days of MVS, when its performance was a sore topic). In 1983, the teddy bear became VM's de facto mascot at SHARE 60, when teddy bear stickers were attached to the nametags of "cuddlier oldtimers" to flag them for newcomers as "friendly if approached". The bears were a hit and soon appeared widely. Bears were awarded to inductees of the "Order of the Knights of VM", individuals who made "useful contributions" to

1323-573: The NOTE program would deliver the email to the SMTP service machine, which would then route it out to the destination site on the Internet. VM's role changed within IBM when hardware evolution led to significant changes in processor architecture. Backward compatibility remained a cornerstone of the IBM mainframe family, which still uses the basic instruction set introduced with the original System/360 ; but

1372-399: 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,

1421-531: The VM/370 Control Program has a number of commands for General Users, concerned with defining and controlling the user's virtual machine. Lower-case portions of the command are optional Starting with VM/ESA Version 2, IBM introduced the chargeable optional feature OpenEdition for VM/ESA Shell and Utilities Feature , which provides POSIX compatibility for CMS. The stand-out feature was a UNIX shell for CMS. The C compiler for this UNIX environment

1470-451: The business of selling computer systems. Melinda Varian provides this fascinating quote, illustrating VM's unexpected success: The marketing forecasts for VM/370 predicted that no more than one 168 would ever run VM during the entire life of the product. In fact, the first 168 delivered to a customer ran only CP and CMS. Ten years later, ten percent of the large processors being shipped from Poughkeepsie would be destined to run VM, as would

1519-401: 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 accessed using the same channel programs as the real disk. A minidisk that has been initialized with a CMS file system

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1568-416: The community-support model of early CP/CMS users. In the meantime, the system struggled with political infighting within IBM over what resources should be available to the project, as compared with other IBM efforts. A basic problem with the system was seen at IBM's field sales level: VM/CMS demonstrably reduced the amount of hardware needed to support a given number of time-sharing users. IBM was, after all, in

1617-497: The community. Bare machine In computer science, bare machine (or bare metal ) refers to a computer executing instructions directly on logic hardware without an intervening operating system . Modern operating systems evolved through various stages, from elementary to the present day complex, highly sensitive systems incorporating many services. After the development of programmable computers (which did not require hardware changes to run different programs) but prior to

1666-456: The development of operating systems, sequential instructions were executed on the computer hardware directly using machine language without any system software layer. This approach is termed the "bare machine" precursor to modern operating systems. Today it is mostly applicable to embedded systems and firmware with time-critical latency requirements, while conventional programs are run by a runtime system overlaid on an operating system. For

1715-517: The free base required a license. As with CP-67, privileged instructions in a virtual machine cause a program interrupt, and CP simulated the behavior of the privileged instruction. VM remained an important platform within IBM, used for operating system development and time-sharing use; but for customers it remained IBM's "other operating system". The OS and DOS families remained IBM's strategic products, and customers were not encouraged to run VM. Those that did formed close working relationships, continuing

1764-518: The limit entirely, and some modern z/VM systems can have as many as 80 processors. The per-VM limit for defined processors is 64. When IBM introduced the System/370 Extended Architecture on the 3081 , customers were faced with the need to run a production MVS/370 system while testing MVS/XA on the same machine. IBM's solution was VM/XA Migration Aid, which used the new Start Interpretive Execution (SIE) instruction to run

1813-399: The machine. Keyboards would later become standard across almost every computer, regardless of brand or price. Computer monitors can also easily display the output of a program in a user friendly manner. For example, one would have to be intimately knowledgeable about a specific early computer and its display system, consisting of an array of lights, to even begin to make sense of the status of

1862-455: The need for efficient use of the 64-bit zSeries made the VM approach much more attractive. VM was also utilized in data centers converting from DOS/VSE to MVS and is useful when running mainframe AIX and Linux , platforms that were to become increasingly important. The current z/VM platform has finally achieved the recognition within IBM that VM users long felt it deserved. Some z/VM sites run thousands of simultaneous virtual machine users on

1911-412: 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

1960-611: The program could be monitored by lights , and output derived from magnetic tape , print devices, or storage . Bare machine programming remains common practice in embedded systems , where microcontrollers or microprocessors often boot directly into monolithic, single-purpose software, without loading a separate operating system. Such embedded software can vary in structure, but the simplest form may consist of an infinite main loop , or "superloop", calling subroutines responsible for checking for inputs, performing actions, and writing outputs. The approach of using bare machines paved

2009-439: The same feature using an OS must route the call to a subroutine, consuming running time and memory. For a given application, bare-metal programming requires more effort to work properly and is more complex because the services provided by the operating system and used by the application have to be re-implemented regarding the needs. These services can be: Debugging a bare-metal program is difficult since: Bare-metal programming

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2058-466: The same format as standard CMS executable modules. Visual editors, such as vi are unavailable, as 3270 terminals are not capable. Users can use ed or XEDIT instead of vi. In the early 1980s, the VM group within SHARE (the IBM user group) sought a mascot or logo for the community to adopt. This was in part a response to IBM's MVS users selecting the turkey as a mascot (chosen, according to legend, by

2107-685: The system using the DASD Dump/Restore program, where the entire contents of a DASD are written to tape (or another DASD) exactly. 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. VM/SP Release 6 introduced the Shared File System which vastly improved CMS file storage capabilities. The CMS minidisk file system does not support directories (folders) at all, however,

2156-650: The user's session. PVM also supported accessing non-VM systems, by utilizing a 3x74 emulation technique. Later releases of PVM also featured a component that could accept connections from a SNA network. VM was also the cornerstone operating system of BITNET , as the RSCS system available for VM provided a simple network that was easy to implement, and somewhat reliable. VM sites were interlinked by means of an RSCS VM on each VM system communicating with one another, and users could send and receive messages, files, and batch jobs through RSCS. The "NOTE" command used XEDIT to display

2205-541: The vector facility (by means of user directory entries). Releases of VM since VM/SP Release 1 supported multiprocessor systems. System/370 versions of VM (such as VM/SP and VM/SP HPO) supported a maximum of two processors, with the system operating in either UP (uniprocessor) mode, MP (multiprocessor) mode, or AP (attached processor) mode. AP mode is the same as MP mode, except the second processor lacks I/O capability. System/370-XA releases of VM (such as VM/XA) supported more. System/390 releases (such as VM/ESA) almost removed

2254-402: The virtual machine. SIE automatically handled some privileged instructions and returned to CP for cases that it couldn't handle. The Processor Resource/System Manager (PR/SM) of the later 3090 also used SIE. There were several VM/XA products before it was eventually supplanted by VM/ESA and z/VM. In addition to RSCS networking, IBM also provided users with VTAM networking. ACF/VTAM for VM

2303-429: The way for new ideas which accelerated the evolution of operating system development. This approach highlighted a need for the following: For example, programs were loaded into the PDP-11 by hand, using a series of toggle switches on the front panel of the device. Keyboards are far superior to these vintage input devices, as it would be much faster to type code or data than to use toggle switches to input this into

2352-424: Was fully compatible with ACF/VTAM on MVS and VSE. Like RSCS, VTAM on VM ran under the specialized GCS operating system. However, VM also supported TCP/IP networking. In the late 1980s, IBM produced a TCP/IP stack for VM/SP and VM/XA. The stack supported IPv4 networks, and a variety of network interface systems (such as inter-mainframe channel-to-channel links, or a specialized IBM RT PC that would relay traffic out to

2401-527: Was subsequently developed for MVT/HASP, MVT/ASP and MVS mainframe operating systems . By September 1979, the network had grown to include 285 mainframe nodes in Europe, Asia, and North America. Unlike the Internet , VNET switched files among mainframes using a store and forward technique. Many of the early connections operated over dial-up phone lines at speeds of 1200 to 2400 bits per second. The addition of

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