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A glossary of terms important to IBM mainframe machines

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M4K:  Another name for the Common Storage Format (see CSF2).

MAAPICS:  Alternate spelling, used in the UK, for MAPICS.

MAC1:  Media Access Control. Generic term for the way in which workstations gain access to transmission media. Most widely used in reference to LANs, in which context IBM uses token passing, and Ethernet uses CSMA/CD.

Mac2:  Apple Macintosh computer.

MAC3:  Mandatory Access Control.

MAC4:  Message Authentication Code algorithm.

MACH:  Unix-derivative operating system developed originally by Carnegie-Mellon University. IBM was consistently rumored to be using it as a kernel able to support OS/2 and AIX1 (see PowerPC), and within Taligent’s projects.

Machine Translation:  IBM’s term for software-assisted translation between languages, such as English to Italian.

Macintosh:  Apple’s PC/workstation which is the only serious non-IBM office workstation. The Macintosh grew its market share on the strength of its user-friendly GUI and its strengths in DTP1. IBM and Apple have various R & D agreements (see Apple). Early 1996 IBM took out a license which enabled it to sublicense the Macintosh operating systems to firms building Macintosh clones based on the PowerPC chip.

Macro1:  A preprocessor (precompiler), and the statements it processes, for Assembler. Generates Assembler instructions and machine instruction mnemonics as well as allowing assembly time conditional logic.

Macro2:  The assembly language for DEC minicomputers.

Macro-level:  The first, now obsolete, method of CICS application programming that used macro calls to interface between the application and CICS. Macro-level worked by allowing programmers to directly modify control blocks, which placed very tight restrictions on the development of CICS. Macro-level CICS programming has been replaced by command-level CICS, and support for macro-level was finally withdrawn with effect from CICS Version 3.2. But, for most, the real date was December 1996, when support ended for CICS/MVS (CICS Version 2.1), because it had been the only supported version of CICS where macro-level would run. Of course, there were non-IBM software products that promise(d) to allow macro-level to run forever under newer versions of CICS.

MADMAN:  Message And Directory MANagement. An Internet standard.

MAESTRO:  An integrated CASE1 environment developed by Softlab and sold originally by Philips. IBM sold it for the RS/6000 until June 1994.

Magneto-optical:  Generic term for an optical storage technology (used in the re-writeable model of the 3995). In the 3995, a combination of heat and a magnetic field is used to create changes in the surface of the recording medium; these changes can be read optically. Re-applying the heat and opposite magnetism reverses the state of the medium.

Magneto-Resistive:  See MR head.

Magstar:  New-generation IBM tape drive announced in April 1995. It’s a generic SCSI device, and initially came with support for AS/400s, RS/6000s, the SP2 parallel systems, and Solaris boxes via a Fast and Wide SCSI-2 interface. Within the IBM ambit, it’s used in the 3590. Key technical features include: serpentine, longitudinal recording technique that enables data to be recorded and read-verified in both directions; 128 data tracks across the tape; second generation magneto-resistive heads which cover 32 tracks at a time and are mounted on a carrier which moves across the width of the tape guided by a track-following servo; pre-written servo track; and a user-written volume control region which contains block and file pointers to enable high-speed, pseudo direct access to blocks or files on the tape. Initially used 10GB cartridges, externally compatible with 3490 cartridges (for use in 3494 and 3495 ATLs) but cannot be read on older devices. ESCON support introduced in March 1996. A new range of Magstar models, announced Sept 1996, includes a Virtual Tape Server which provides some pioneering technology for stacking multiple tape volumes on a single cartridge.

Mail Exchange:  Formerly, an IBM public e-mail service on the Information Network (see IN). X.400 support announced November 1991.

Mail LAN Gateway:  OS/2 software, known as IMLG/2, which enables incompatible e-mail systems to exchange files and mail. Supports any-to-any communication among cc:Mail, OfficeVision, PROFS, and any SNADS-compliant e-mail application. Announced October 1992. Moved to the Soft-Switch division of Lotus November 1996. Lotus has since completely scrapped Soft-Switch and its products.

Mainframe:  Mainframes used to be defined by their size, and they can still fill a room, cost millions, and support thousands of users. But now a mainframe can also run on a laptop and support two users. So today's mainframes are best defined by their operating systems: Unix and Linux, and IBM's z/OS, OS/390, MVS, VM, and VSE. Mainframes combine four important features: 1) Reliable single-thread performance, which is essential for reasonable operations against a database. 2) Maximum I/O connectivity, which means mainframes excel at providing for huge disk farms. 3) Maximum I/O bandwidth, so connections between drives and processors have few choke-points. 4) Reliability--mainframes often allow for "graceful degradation" and service while the system is running.

Main System:  The system designated to received most of the RRSF communications on a multisystem RRSF node.

malloc:  The default memory allocator subsystem in AIX1.

Mammoth-2:  8mm tape drives used in 7334.

MAN:  Metropolitan Area Network. Generic term for the logical and physical evolution from LAN technology. A MAN provides a network in scale somewhere between a LAN and a WAN. Typically a MAN will cover about 50km, run at 100-200Mbps+, and mix different types of traffic – voice, data, image, etc. FDDI was a hot favorite to become the standard MAN technology, but was soon replaced by ATM. Standards for MANs are continually being developed by the IEEE and ANSI.

Managed System Services:  iSeries 400 SystemView software, introduced September 1993, which allows multiple unattended iSeries 400s to be managed remotely from a mainframe (including application of PTFs, remote IPL, etc). The mainframe needs to be running software which supports SNA/MS2 (e.g., NetView DM). An alternate approach is to use an iSeries 400 to manage other iSeries 400s. See System Manager for details.

Managed user ID association:  Relationship between two user IDs, where the managing ID can run RACF commands under the authority of the managed ID, but not vice versa.

Management Buyout:  See MBO.

Management Central:  Part of Operations Navigator which, in turn, is part of OS/400. A GUI for remotely managing iSeries 400 systems, from a Web browser, PDA with wireless modem, even from a cell phone.

Management Class:  One of the SMS1 storage management classes. Management Class defines the backup/recovery and migration/recall requirements of a dataset1. In England the phrase has political significance and should be used with great caution.

ManageWare/400:  AS/400 SystemView software, introduced September 1993, which administers the distribution of software from an AS/400 to PCs and PS/2s. Administrators can manipulate nodes, register and log package distribution, and manage licenses. Part of IBM’s strategy of promoting the AS/400 as a server. Withdrawn December 1997.

MAP1:  Manufacturing Automation Protocol. General Motors’ standard for factory floor communications which at one time looked to be heading for industry-standard status, but is now in the doldrums. It’s an implementation of the ISO OSI seven layer model, which uses broadband, IEEE 802.4, token-bus LANs. MAP connection to z/VM was available from IBM, and MAP network management is supported in IBM’s OSI/CS product. Manufacturing Automation Protocol VM Support was replaced May 1990 by OSI/Manufacturing Messaging Services for VM, but it was withdrawn May 1992. There was also an OS/2 version which was not withdrawn until 1998 in a Y2K roundup, but support had ended years before.

MAP2:  Maintenance Analysis Procedure. Documentation used by IBM service personnel for hardware maintenance. It has a step-by-step procedure for tracing a symptom to the cause of a failure.

MAP3:  Migration Assist Program. Defunct IBM scheme which helps people move from an old system to a new one, typically by offering a very good trade-in deal on the old machine. MAP has been used for two main purposes: first to placate people who’ve bought a machine which has almost immediately been obsoleted, and secondly to keep up sales of an about-to-be-superseded line just prior to the introduction of the successor.

MAPI:  Messaging/Mail Application Programming Interface. Messaging standard promoted by Microsoft for joining desktop computing programs to a messaging service. Supported by IBM in its IBM WorkGroup product.

MAPICS:  Manufacturing, Accounting, Production and Control System. MRP system originally developed for the System/36, then made available on the System/38 and AS/400 for CIM1 applications. In a March 1993 agreement with Marcam Corporation, IBM stopped marketing MAPICS. Also spelled MAAPICS.

MAQ:  Maintenance Agreement Qualification letter. A certificate of quality issued by IBM after a detailed inspection of a machine. The MAQ states that IBM agrees to continue to maintain the machine under a new owner, or at a new site. An MAQ lasts for six months and is very useful for those buying and selling second-user machines. In the late 1990s, there were some changes, resulting in two versions becoming available: a General Maintenance Agreement Qualification, and a Tailored-Maintenance Agreement Qualification.

Marcam:  The company which developed the MAPICS software.

Market basket:  IBM discount scheme in which IBM discounts products by offering you a credit of up to 10% of the product’s value: you can spend this credit on other IBM products selected from the current market basket. It’s not a bad deal, but you have to make sure that the products are ones that you would have bought anyway – what’s in the basket is the stuff IBM wants you to have, rather than the things you’d choose if they weren’t in the basket. The Market Basket term was dropped when the generic term Market Basket Analysis came into popular use in the mid-1990s.

Marketecture:  A wonderful coinage to describe grand designs whose existence owes more to the creative intellect of marketers than to the industry of product developers. IBM is the past master at creating marketectures, outdoing even the people who write manifestos for politicians. See, for example, ASA, Common Cryptographic Architecture, CDRA, CSA3, DCA, DIA, ESA, FAA, FBA, FOCA, GOCA, GTA, IAA, IIA, IOCA, MCA, OCA1, OCA2, OIAA, OSA1, PAA, PTOCA, SAA, SMA, SNA, UIA, etc, etc, etc.

Markup language:  A notation for identifying the elements of a document to enable each element to be formatted, and displayed. See HTML, XML, SGML.

Master catalog:  The z/OS catalog where the search begins for a dataset. cf. User catalog.

Master Primary Dataset:  The first dataset activated in the primary RACF database.

Matsushita:  Very large and diversified Japanese industrial company which, among other things, has been the OEM manufacturer of IBM’s Japanese market PCs, and supplier of the optical disks in the 3995. It also made some PS/2s for IBM in Taiwan and in the USA. But, best known by its Panasonic brand name.

MAU:  Multi-station Access Unit as in the defunct 8228. Ring wiring concentrator at the center of a TRN star-wired network. A passive device (a small box with 8 or 16 connectors, and relays acting as by-pass switches) which, among other things, enables a physical star network to function as a logical ring network (thereby allowing the wiring from an existing terminal network to be used for the TRN). MAUs can be connected to create bigger rings with up to 256 devices. The 8228 MAU has minimal logic supplying some capability for detouring round failed devices (it listens out for the I’m alive signal from the workstations, and automatically disconnects a dead workstation using a by-pass relay). See also 8230.

Maximum Strategy Corp:  IBM partner in a program to develop HIPPI attachment of disk arrays for scientific and number-crunching applications.

Maximum Transmission Unit:  See MTU.

Mb1:  See Megabit.

MB2:  See MegaByte.

MBA:  Memory Bus Adapter.

MBCS:  Multi-Byte Character Set. Coding system for characters where each character requires more than one byte to represent it. Required for languages with more than 256 characters that need to be represented. English is just the reverse with only 26 letters, 10 digits and a small set of punctuation and no accent marks. cf. SBCS, DBCS.

Mbit:  See Megabit.

MBNLQ:  Menu-Based Natural Language Query program. PC and PS/2 end-user tool which converts English language screen prompts into SQL for up-loading to an AS/400 or System/3x. Obsolete PRPQ2.

MBO:  Management BuyOut. Existing management of a company buy it from its owners.

Mbps:  Megabits per second.

MBRS:  Mobile Business Recovery Services. An IBM foray into disaster recovery. Consisted of an AS/400 on the back of a truck. Obsolete.

MBS:  Maximum Burst Size.

Mbyte:  See Megabyte.

MC:  See Management Central.

MCA:  MicroChannel Architecture (MCA). The peripheral bus introduced with the first PS/2s. The MCA was a proper channel architecture incorporating lots of the features for which add-in cards were necessary on the PC. MCA did not have the immediate impact that IBM wanted, and the compatible vendors developed an alternative (EISA) in the hope of gaining control of the standard for PC add-ons. In the end, EISA and SCSI became the low and high end workstation standard, respectively, for hard disk and a few other devices. But it was PCI that replaced both MCA and ISA for all other cards in the workstation. AGP has since become the standard for video cards. And, of course, there is USB for external devices. MCA was also used, for a time, as the standard channel on the RS/6000. See also MCDA.

MCCU:  Multisystem Channel Communication Unit. Same as MSCU.

MCD:  Management Consultancy Division. A division of IBM set up in August 1991 to sell consultancy services in the market dominated by the likes of McKinsey & Co and Booz Allen and Hamilton (from whom MCD recruited its head). Naturally, it failed miserably given the difficulty of persuading prospects that a company which had, at the time, made such a dog’s breakfast of its own fortunes would be a good company to advise the prospect’s organization. See also Know How, Global Services.

MCDA:  MicroChannel Developers’ Association. Now defunct consortium set up October 1990 by IBM and various PC manufacturers to promote IBM’s MicroChannel architecture (MCA). Aimed at reviving the moribund fortunes of the MCA standard whose failure to take off was partly attributable to the absence of a second source for MCA machines (at the time that the MCDA was set up, 94% of installed MCA-equipped machines were IBM-made). See also EISA, PCI.

McDATA:  McData Corporation. IBM expanded its reseller agreement with McDATA in March 2001 to include the complete Enterprise-to-Edge family of SAN products.

MCGA:  Multi-Color Graphics Array. The low-end color video monitor adapter for IBM’s early PS/2 series machines.

MCI:  MCI Communications Corp (the letters MCI originally stood for Microwave Communications Inc – but it’s just MCI these days). Major US long-distance communications carrier of which IBM acquired a large chunk in 1985 in exchange for bits of SBS and three satellites. During 1988 MCI bought itself back from IBM.

MCM1:  MultiChip Module. Standard hardware packaging, including the processor, for eserver zSeries 900, originally introduced in the G5 System/390.

MCM2:  Multichip Ceramic Module. Technology used in some RS/6000s that had interesting implications, such as the requirement that memory be installed in pairs.

MCS console:  A non-SNA device defined to z/OS, used to enter commands and receive messages, that is locally attached to a z/OS system.

MCU1:  Magnetic Card Unit.

MCU2:  Modular Cooling Unit. Used on the eserver zSeries 900.

MD2:  Hashing algorithms developed by RSA Security to create a 128-bit hash value from a 64-bit block.

MD4:  Hashing algorithms developed by RSA Security to create a 128-bit hash value from a 64-bit block.

MD5:  Hashing algorithms developed by RSA Security to create a 128-bit hash value from a 64-bit block.

MDp:  Message Driven processor. An IBM PRPQ2 originally from Early, Cloud & Company. See Messaging. Replaced by the MQSI Agent for CICS

MDQ:  Market Driven Quality.

Measured Usage:  The method of charging for software based on the monthly usage. Same as Usage pricing.

Media Access Control:  See MAC1.

MediaStreamer:  Specialized RS/6000 storage product, and the AIX1 software to run it, for storage and delivery of multiple video streams from a single copy on a RAID system. Announced December 1994. Withdrawn June 1998.

Megabit:  1,048,576 bits. Abbreviated as Mb.

Megabyte:  Roughly one million bytes – actually 1,048,576 bytes. Abbreviated as MB.

MegaFLOPS:  One million FLOPS.

Megaplex:  A processor complex formed by connecting together sysplexes, possibly distributed over a number of sites.

Member:  A RACF user belonging to a group.

Member Profile:  A RACF profile storing the security level information for, and definition of, a member.

Member System:  Any z/OS system image in an multisystem RRSF node.

Memory-based computing:  The notion that all data and programs should be held in some form of immediate access semiconductor memory (main store or expanded storage). Holding data in memory obviates the need for time-consuming channel transfers and gives very substantial performance benefits. IBM benefits too because you need to buy large amounts of memory on which to base your computing. DFSMS and ESA were the key initial architectures designed to make memory-based computing possible. Note that memory-based computing has the effect of changing the large system from a read-dominated environment to a write-dominated environment – hence the emphasis in IBM’s then plans of features such as the 3990 DASD Fast Write.

Merchant server:  In the SET architecture this is a Web server that offers catalog shopping.

Mercury:  An architecture cum technology (announced March 1994) from Legent and IBM. Used SNMP standards to allow management of distributed applications from a central (probably mainframe) platform.

Merge:  The combining of two or more sorted files into a single file. One of the two main capabilities of a sort/merge program. See also DFSORT.

Merlin:  OS/2 Warp development to upgrade OS/2’s capabilities, including multimedia, games, networks, security, speech recognition, Internet capabilities, and Windows 95 compatibility.

Merva/370:  Message Entry and Routing for Various Applications. A somewhat obscure bit of software used for connecting to the European S.W.I.F.T interbank telecommunications system. Available in various incarnations for the mainframe, PS/2, AS/400, and RS/6000. Announced June 1988. See

MES:  Miscellaneous Equipment Specification. An RPQ on-site upgrade.

Message Queue Manager:  MQM. See MQSeries.

Messaging:  Generic term for a technique (aka Transactional Messaging) for implementing distributed systems. Messages are sent to a number of different processes in a distributed system; the processes access queued messages, generate new messages, and carry on until the application is finished. In effect it’s an architecture for high-reliability store and forward systems. The technique simplifies the writing of program to program communications by hiding the underlying protocols (which also makes it open and system-independent). See also CPI-M, MQI.

Metaphor:  US company (a Xerox spin-off) which developed a proprietary WIMP-type workstation linked to a file/database server accessing mainframe VSAM files and databases. Metaphor struck up an agreement with IBM mid 1988 to port the interface and database server to the PS/2 environment – which it did in the Data Interpretation System (DIS) which IBM marketed. By October 1991 IBM had bought Metaphor lock, stock, and interface, but the company continued to run under its own name and management. However, mid 1994, IBM announced that the company would close by the end of the year and that its staff would be absorbed into the IBM body corporate. See also Patriot Partners.

MFI:  MainFrame Interactive. MFI workstations is IBMspeak for dumb(ish) terminals such as the 3270 and 5520 families. The term died in favor of NPTs (Non Programmable Terminals) but that too is a distant memory.

MFLOPS:  MegaFLOPS. One MFLOPS is one million floating point operations per second. See FLOPS.

MFS:  Message Format Service. An editing facility found in IMS1 that allows applications to deal with simple logical messages rather than device-dependent data. This has the advantage of simplifying application development. IMS TM equivalent of the CICS BMS1. Famous for having one of the all-time dreadful manuals.

MFT:  Multiprogramming Fixed Tasks. Ancient forerunner of z/OS.

MgW:  See ManageWare/400.

MHPG:  Multiple High Performance Guest. See VM/MHPG.

MHS:  Message Handling System/Service. A generic ITU-T term for message communication services of the store-and-forward variety. Under X.400, MHS enables connections to be made between fax, telex, teletex, and electronic mail services.

MIB:  Management Information Base. Generic term (often used specifically in relation to the SNMP management protocol) for the database of the objects managed in a network – usually a LAN. IBM tends to use the term repository to refer to the same thing. See also CIB, EIB, Resource Object Data Manager.

Michigan Terminal System:  See MTS2.

MICR:  Magnetic Ink Character Recognition. A technology best known for its use to read those funny shaped numbers on checks and other bank documents. Supported by IBM on the 3828, and via a special interface on the 3835. MICR/OCR Support is an element of z/OS.

Micro CADAM:  CAD software sold by IBM’s CADAM subsidiary. Available on a wide range of workstations including RS/6000 and Sun. CADAM has been merged with CATIA and the CADAM name has gradually disappeared. See CATIA.

MicroChannel:  See MCA.

MicroChannel 370:  Desktop mainframe models announced September 1990. Basically re-named 9371s with some extra features, mainly to support remote operation, including remote installation of firmware, improved system recovery, and more DASD. Not a lot was ever heard of them apart from the announcement.

Microcode:  Although it can have very specific alternative meanings, its most common usage is as a synonym for firmware.

Micrografx:  Company with which IBM set up an alliance in April 1991 after IBM fell out with Microsoft. Micrografx and IBM worked jointly on developing ways of improving Presentation Manager, and of making Windows applications run better under OS/2.

Microkernel:  Now a generic term for a Unix kernel kept as small as possible by making files systems and device drivers external processes. But, it once was a core operating system under development by IBM for use on the PowerPC. It was built on top of the Mach operating system kernel, and designed in a way which allowed various personalities to be grafted on top, to create a wide range of different environments. Promised personalities included Unix, Windows, MS-DOS, OS/2, Macintosh, and Taligent. Originally known as the Workplace OS and Workplace Microkernel before it became Microkernel.

MicroMASTER:  1992 vintage processor card that fitted into the MicroChannel on a PS/2 and transmogrified it into a brand new high-powered 32-bit machine. Developed by AOX Corp in conjunction with IBM and sold by IBM. Obsolete.

Microsecond:  1/1,000,000 of a second.

Microsoft:  The company which made the shrewd move of persuading IBM to use its DOS operating system for the IBM PC. Even more amazing is the fact that the fateful 1981 meeting with IBM was intended to discuss Microsoft’s BASIC, when Bill Gates got wind of the fact that the negotiations with Digital Research for CP/M were not going well. And he knew of another Seattle developer who had created an operating system by reverse engineering CP/M and was confident he could acquire the rights. The rest is history. Microsoft is now huge and influential, and has appeared on many occasions to be able to dictate IBM’s product strategies in the PC and LAN areas. Microsoft and IBM were once a happy couple, but the relationship started looking distinctly shaky mid-1990, when Microsoft started to nurture its own Windows 3.0 offspring, at the expense of their joint child, OS/2. The once happy couple are separated now: IBM has custody of OS/2 (although it had to pay royalties to Microsoft until 1998); Microsoft has DOS and Windows; and since September 1993 they no longer share information about any operating system developments. Microsoft has also taken over IBM’s role as the computer company you love to hate. And Bill Gates has actually found time for a wife and children by moving into Microsoft’s Chief Technology Officer position.

Microsoft Transaction Server:  See MTS1.

MIDA:  Message Interchange Distributed Application. European Computer Manufacturers’ Association (ECMA) standard for text interchange.

Middleware:  Defies definition, although one slightly jaded view which emanated from the lips of an IBM executive is Any run-time code which is not yet in the operating system. For a time, like the client/server that preceded it, a majority of the world’s software was suddenly middleware. Its primary role is to provide connectivity services between platforms. There are numerous types: messaging middleware (e.g., MQSeries), database middleware (e.g., IBI EDA/SQL).

Migrate:  To move from one version of a system to another. Major migrations always used to send a chill down the spine of the most battle-hardened DP manager, since the result was almost inevitably two years of total chaos before the new system works as well as the old. These days, IBM is a lot better at ensuring that migrations are a lot less painful than they used to be.

MI head:  Magneto-Inductive head. Once the standard technology for tape and disk head. See also MR head.

Millennium:  A highly automated distributed system developed by Microsoft’s research group.

Millennium Runtime Windowing:  IBM tool used for z/OS short-term Y2K fixes. It is used to assess Y2K problems at execution time, allowing a predominantly automated fix to the load modules.

MILNET:  The military network that was originally part of ARPAnet. It was partitioned from ARPANET in 1984.

MIME:  Multipurpose Internet Mail Extensions. An encoding format which allows e-mail messages containing a variety of media forms (audio, video, image, and text) to be sent across the Internet.

Mimix:  Hot standby facility on the iSeries 400. Works by mirroring the main database or nominated files in read-only form on a second system. Bought in by IBM from Lakeview Technology, NY.

MIMX:  See Mimix.

Mindspan:  IBM Mindspan Solutions. Works with Lotus LearningSpace and IBM Learning Services to create a training function within an organization.

Minicomputer:  IBMspeak for a machine that’s not a PC, but is small enough to hide in a departmental budget.

Mini-disk:  z/VM storage unit. Each virtual machine running under VM is given space on a real disk in the form of one or more mini-disks. Each user gets their own virtual machine when they logon, so that means each user gets their own mini-disk.

MIPS:  Million Instructions Per Second, (or Meaningless Indicator of Processor Speed, Many Important Selling Points, etc). A crude and not very meaningful way of expressing raw computer power. Not often used by IBM, which prefers to use ITR to express the power of a machine by comparing it with another machine in the same range. One of IBM’s rare forays into the world of MIPS gave what it claimed to be audited debit-credit figures showing that an IBM MIPS is about 3.24 times the size of a DEC MIPS. Pundits reckon that a mainframe MIPS is worth about 15 Unix MIPS. See also BIPS.

Mirroring:  The technique of constantly maintaining a parallel copy of critical datasets, so that the duplicate data can be used if there is a problem with the main data. See Dual copy, Mimix, XRF.

MIS1:  Management Information Systems. Systems designed to provide information to management on an ad hoc basis. Largely replaced by EIS and DSSs; see DSS1, EIS2

MIS2:  Management Initiated Separation. IBMspeak for the process of being given the old heave-ho by the jolly blue giant, which gives the lie to the long-cherished belief that you can’t be fired for choosing IBM.

MIT:  Massachusetts Institute of Technology.

MLC:  Monthly License Charge. Superseded in most cases by the GMLC. See also FMLC, IMLC.

MLE:  Millennium Language Extensions. IBM product for changing COBOL and PL/I applications to handle year 2000 dates. MLE is integrated into COBOL and PL/I compilers and automates date century windowing. It does not actually cure the problem but will provide some extra time for non-critical applications. See Y2K.

MM:  MultiMode.

MMF:  MultiMode Fiber.

MMR:  Modified Modified Read. Proprietary IBM compression algorithm used in its image processing systems. User pressure forced IBM to edge away from MMR to the ITU-T Group 4 fax standards, but IBM keeps announcing new products that support both.

MMX:  MultiMedia eXtensions (MMX). A set of instructions Intel added to its iAPX-86 chips in March 1996. The MMX additions are aimed specifically at speeding up multimedia and communications applications, and enabling multiple data elements to be processed in parallel through Single Instruction Multiple Data techniques.

MNP:  Compression and error detection algorithm for modems. Invented by Microcom and implemented as a de facto standard by many manufacturers.

MNPP:  Multi-protocol Network Processor Program. The software in the 6611, now called MPNP.

MNPS:  MultiNode Persistent Session. An LU-LU session on the mainframe that survives a failure of VTAM, the operating system or the hardware.

MNS:  Managed Network Service. A VANS/VADS provided by IBM UK before it all got sold to AT&T. See Global Network.

MO:  See Magneto-Optical.

MO:DCA:  Mixed Object: Document Content Architecture. IBM architecture for mixed documents (text + image + graphics etc). The replacement for the 3270 datastream for graphics-oriented terminals. Crucial to OfficeVision and ImagePlus; MO:DCA specifies the interface to OfficeVision.

MO:DCA-P:  MO:DCA – Presentation.

Mobile Notes:  Used with Domino Everyplace, provides access to e-mail, calendar, directories and Domino-based applications from handheld devices like PDAs and WAP phones.

Mobile Services for Domino:  A server that acts as a proxy and otherwise provides secure communications from Domino to Mobile Notes. See also proxy server.

Model group:  The traditional basis of IBM’s method of charging for software; processors are grouped according to their power, and the more powerful the processor, the more you pay IBM for software. It’s grotesquely unfair – a bit like paying more for your electricity if you live in a big house, even if you only use the same amount as someone living in a small house. Usage pricing has replaced model group pricing in many situations. See also User-based pricing.

Modeling:  See profile modeling.

Modem:  MOdulator-DEModulator. Device which modulates a digital signal into an analog form and demodulates an analog signal into a digital form (e.g., a 0 into a high tone, and a 1 into a low tone), usually for transmitting and receiving binary data over telephone lines and cable television wiring. IBM modems tend to be expensive, but well endowed with facilities for reporting their activities to IBM network management software. Known by AT&T as a dataset2.

Modular Switching Hubs:  Chassis-based hubs (e.g., IBM 8260 or 8274) that accept multiple types of switching module such as Token Ring, Ethernet, Fast Ethernet, ATM2, FDDI.

MOF:  The OMG’s Meta Object Facility defines a meta-metamodel which is useful for reconciling different metamodels (such as those of programming languages).

MOLAP:  Multi-dimensional On-Line Analytical Processing.

MOM:  Message Oriented Middleware. For example, MQSeries.

MOMA:  Message Oriented Middleware Association. An acronym (shared with the altogether more interesting Museum of Modern Art in Manhattan) for the organization which promotes MQSeries.

Monthly License Charge:  See MLC.

Mosaic:  PC software from the National Center for Supercomputing Applications at the University of Illinois that allows users to browse Web servers on the Internet. No longer commercially available.

MOSP:  Multiple Operating System Pricing. Pricing schedule introduced in June 1992 for mainframe software which marginally reduces the costs of software under PR/SM.

MOSS:  Maintenance and Operator SubSystem. Subsystem which monitors the operation of the 37xx communications controller. See MOSS-E.

MOSS-E:  Maintenance and Operator SubSystem Extended. A subsystem of the 3745 Communication Controller. MOSS-E operates independently of the rest of the controller. It is used to load and supervise the controller.

Motif:  The interface to AIX1/Unix developed by the OSF. It’s an amalgam of the IBM/Microsoft Presentation Manager, DEC’s DECwindows, and HP’s New Wave, and was built by a joint DEC/HP team. From the user point of view, it’s the same as Presentation Manager. Consists of a Style Guide (a similar concept to the SAA CUA1), and a toolkit which implements the style guide in an X-Windows environment. Used as the basis of AIXwindows.

MOTIS:  Message Oriented Text Interchange System. ISO standard for text transfer.

Motorola:  Semiconductor company which, among a diverse range of products, made the 68000 family of chips used for years in the Apple Macintosh, and the odd IBM machine. October 1991 Motorola, IBM, and Apple set up a joint project to work on a new chip which eventually became the PowerPC. Today, the PowerPC runs both the eserver pSeries and the Mac.

Move Page:  Mainframe machine instruction supported by z/OS beginning October 1989. Used to transfer data between expanded and central storage. Originally implemented as a new ESA instruction using the DAT facility. Move Page is used by Hiperbatch. Made available for z/VM in September 1991. A standard feature of the zSeries 900. See also Page.

MP:  MultiProcessor. Mainframe configuration with two or more CPUs, each with its own I/O, but under the control of a single operating system.

MP3:  See MPEG.

MPC1:  See MultiPath Channel.

MPC2:  AIX Multiprotocol Client.

MPEG:  Motion Pictures Experts Group. International standard for digital video and audio compression for moving images. MPEG-I Audio Layer III is the familiar MP3 format used to compress audio for transmission over the Internet and in portable players that are the equivalent of the Sony Walkman.

MPF:  Message Processing Facility. A facility in z/OS that controls message display and message processing, typically to suppress unnecessary system messages. A faltering step towards automated operations.

MPG:  Multiple Preferred Guest. Hardware feature first introduced on the 3090E, which gave support for up to six preferred guests under VM/XA SP.

MPNP:  Multi-Protocol Network Program. The software in the 6611. Updated in February 1994 with better response times, lower times for data link switching, improved support for SNA, NetBIOS, APPN network node, and Banyan Vines, and in September 1994 with DLSw traffic prioritization, and expanded connectivity. March 1996 it acquired ANR, RTP, and ARB.

MPOA:  Multi-Protocol Over ATM2.

MPP1:  Message Processing Program. See also IMS TM.

MPP2:  Massively Parallel Processing. Although often used as a generic term for parallel processing systems, more strictly it means systems in which a number of processors, each with its own memory, are connected together. Applications are able to run across a number of processors if necessary. MPP systems require special operating systems and applications software capable of supporting the required parallelism. See also Symmetric multiprocessing.

MPSX/370:  Mathematical Programming System eXtended/370. Linear programming (a mathematical not computing technique) implementation under z/VM and z/OS. Vector support is available, but no eserver zSeries 900 supports vector coprocessors or instructions. Still available, though there has not been a new release since 1990.

MPTF:  Multi-Protocol Transport Feature. IBM’s common transport mechanism that allows multiple high-level communications protocols to run over a range of lower-level ones. MPTF was the first implementation of MPTN in VTAM in April 1993. aka AnyNet.

MPTN:  Multi-Protocol Transport Networking. The architecture underlying the lower (Common Transport Semantic layer) levels of the Networking Blueprint. The first MPTN products (March 1993) supported TCP/IP across SNA and ran on z/OS and OS/2. MPTN was later adopted by The Open Group as a standard.

MQe:  See MQSeries EveryPlace.

MQI:  Message Queuing Interface. Standard within the Networking Blueprint for simplifying the transmission of transactions across a (possibly multi-vendor) network. The MQI is a high-level API which allows applications to communicate asynchronously via message queues. Enables programs in a heterogeneous network to communicate independently of the underlying communications protocols. First implemented in the CICS Message Queue Manager product in z/OS. See also Messaging, MQSeries.

MQM:  Message Queue Manager. See MQSeries.

MQSeries:  Messaging and Queuing Series. Set of products and standards (developed jointly by IBM and Systems Strategies Inc (now Apertus Technologies Inc)), and announced in March 1993 for the development of client/server-type TP applications based on the MQI. Provides a queuing infrastructure that sits on various systems in a client/server environment, and stores and forwards messages independently of the systems at each end of the communication. It can provide a single interface across a range of very different systems, including AIX1, z/OS, OS/2 Warp, OS/400, TPF, z/VM, VSE/ESA, 469x OS, Apple MacOS, DYNIX/ptx, Compaq NonStop Kernel, Compaq OpenVMS on VAX and Alpha, Compaq Tru64 Unix, Data General DG/UX, PC-DOS, HP-UX, HP 3000 MPE/ix, Hitachi, Java, Linux on Intel and zSeries 900, Windows 3.1/9x/2000/XP, NT1 on Intel and Alpha1, NCR (aka AT&T GIS) Unix, Pyramid DC/OSx, Siemens Nixdorf SINIX, SCO OpenServer, NUMA-Q, SCO UnixWare, SGI, Stratus VOS, Sun Solaris on Sparc and Intel, Unisys ClearPath OS 2200, Unisys A. See also MOMA.

MQSeries EveryPlace:  Intended to provide the security and guaranteed delivery approach of MQSeries to mobile users and the devices/computers they use. Despite the fact that they normally connect via an insecure, fragile network. Announced April 2000.

MQSeries Financial Services Edition:  See MQSFSE.

MQSeries Integrator:  See MQSI.

MQSeries WorkFlow:  A workflow management system, replacing FlowMark and based on MQSeries. A WebSphere Application Accelerator.

MQSFSE:  MQSeries Financial Services Edition. Business processes implemented on the MQSeries platform, focusing on e-business and CRM. A WebSphere Application Accelerator.

MQSI:  MQSeries Integrator. The MQSI Agent for CICS replaces MDp and attempts to minimize the migration effort. A WebSphere Foundation Extension.

MRC:  Monthly Rental Charge.

MR head:  Magneto-Resistive head. Type of tape/disk read head (used in the 3514, 3590, 3480/3490, 9340, and 3390-9, and several of IBM’s OEM offerings). The advantage is that it can tolerate lower signal/noise ratios, and can be made very small for reading very high-density media. See also MI head.

MRI:  Machine-Readable Information. Literally, data that could be input to a computer. Really meant to signify that electronic information is available for download or on optical or magnetic media, not on paper.

MRO:  Multi-Region Operation. A mechanism by which different CICS address spaces and regions in the same CEC can communicate and share resources (without using VTAM) to create a CICSplex. Also enables CICS to be subdivided into more than one address space, with the consequent easing of restrictions on the amount of virtual storage available. IBM’s strategic route for multi-CPU exploitation.

MRP:  Manufacturing Resource Planning or Materials Requirements Planning. Generic term for software used to control manufacturing processes. See also CATIA, ENOVIA.

MRQ:  Message ReQueuer. IMS TM utility which can be used to select messages from the IMS TM or system log, and move them to IMS TM message queues. Helps IMS TM recovery.

MRTD:  Machine Readable Travel Document. A joint venture between IBM and Statistica that allows government agencies to generate, issue, inspect and manage the visa/passport process domestically, and in foreign embassies and consulates. IBM provides system and peripheral hardware and software, while Statistica provides its Statisticard system product and related training/support services. MRTD is a computerized image system that produces tamper resistant, filmless, identification documents on-site.

MRU:  Most Recently Used. Generic (non-IBM) term typically used to refer to DASD caching strategies.

MS:  See Microsoft.

MSAU:  Another name for the MAU.

MSC1:  Multiple Systems Coupling. A feature in IMS TM that allows dispersed IMS TM systems to communicate.

MSC2:  Memory Storage Controller.

MSCU:  Multiple-System Coupling Unit. The 3088. Also known as MCCU.

MS-DOS:  Microsoft-Disk Operating System. An enormously successful disk operating system (there were well over 100M MS-DOS licenses at its peak) for microcomputer systems from which IBM’s PC-DOS was derived. Beginning with Windows 95, Windows became an operating system, rather than an operating environment that ran on DOS. But Windows 95, 98 and Me still had a lot of DOS inside them. And it was not until Windows XP that a clean break was made, and the non-DOS Windows NT/2000 took over.

MSHF:  Matrix Switch Host Facility. NetView application program providing central support for the 3728 matrix switch. Replaced by MSHF2, which was withdrawn January 1996.

MSHP:  Maintain System History Program. VSE/ESA program, first introduced in 1979, which tracks all products and services on a system.

MSMQ:  Microsoft Message Queue (originally codenamed Falcon), Microsoft’s MOM product which is built into Windows. Microsoft MSMQ-MQSeries Bridge provides interoperability with MQSeries.

MSN1:  Multisystems Networking. VTAM or TCAM facility supporting communications sessions between SNA host nodes (mainframes). New name for MSNF.

MSN2:  Microsoft Network. Originally a proprietary network like AOL, but now a Web site at Like AOL, attempting to provide organization in a world of (Internet Web site) chaos.

MSNF:  Multisystem Networking Facility. Now known as MSN1.

MSO:  Main Storage Occupancy.

MSS1:  Mass Storage System. Hardware subsystem for storing very large amounts of archive data, typically by using some kind of jukebox mechanism to retrieve discrete data cartridges. IBM abandoned this market for a long time, preferring to encourage people to keep all their data on-line on DASD, but re-entered it with the 3495 which has since been replaced by the 3494. See 3851, ATL.

MSS2:  See Multiprotocol Switched Services.

MSU:  Millions of Service Units.

MS-Windows:  Microsoft Windows. See Windows.

MTA:  Message Transfer Agent. See X.400 MTA.

MTBF:  Mean Time Between Failures. The average value of the lengths of time between consecutive failures under stated conditions of a system.

M Technology:  The current name for what used to be called MUMPS.

MTO:  Master Terminal Operator. Software enabling a terminal to control a subsystem, e.g., IMS/MTO, CICS/MTO. The equivalent of the operating system’s Operator’s Console.

MTS1:  Microsoft Transaction Server (originally codenamed Viper) is said to combine the features of a teleprocessing monitor and an ORB, thus qualifying as an OTM. It is closely linked to COM. Beginning with Windows 2000, MTS functionality is included in COM+.

MTS2:  Michigan Terminal System. A non-IBM 360/370 batch and on-line operating system once used in a few large post-secondary education institutes in North America and the U.K. As the name implies, originally developed in 1967 at the University of Michigan for the System/360 Model 67, as a stop gap until TSS became available from IBM. When TSS never really came at all, other sites eyeing the Model 67 for its unique virtual storage capability installed MTS as well. MTS was built with paging in mind, initially using drums for high speed paging, then fixed head disk. Instead of being sold, each MTS site committed a certain amount of manpower to continuing development on the operating system. A lot of MTS concepts ended up in TSO. One unique feature was a common command language for both on-line and batch. A full screen editor was added in 1973. A joy to use, but a pig to operate. Disappeared by the 1990s as universities got rid of their academic mainframes.

MTTR:  Mean Time To Recovery or Repair. The average time required for corrective maintenance. See MTBF.

MTU:  Maximum Transmission Unit. How big a block of data can be. Typically used when discussing Ethernet.

MULC:  Measured Usage License Charge. See Usage pricing.

MULIC:  Model Unique Licensed Internal Code – the firmware that controls an iSeries 400. IBM insists that the firmware must be licensed to a specific processor and frame, so that if a machine is upgraded by a third party, a new model-unique tape will have to be obtained from IBM.

Multi-Byte Character Set:  See MBCS.

Multichip Ceramic Module:  See MCM2.

MultiChip Module:  See MCM1.

Multidrop:  A communications technique in which a number of devices share a channel, but transmit on it one at a time.

Multimedia:  Systems which use digital technology to mix audio, visual, and other information. July 1990, IBM formed a new Multimedia Division but it disappeared in the intervening years. See also AVC, CED, Fireworks Partners, Kaleida, M-Motion, Linkway, Person to Person, ScriptX.

Multimodal user interface:  An IBM computer interface that responds to human voice and gesture. IBM’s ViaVoice speech recognition software interprets vocal commands. An embedded camera sends visual information to a machine vision system that tracks movement and gestures. Special algorithms combine and interpret the user’s actions. This effectively eliminates the need for keyboards, monitors, mouse, and wires. Announced September 1997. This is part of an arena called Natural Computing. On its Web site, IBM calls it Ease of use.

Multinode Persistent Session:  See MNPS.

MultiPath Channel:  IBM’s highly optimized Layer 2 channel-protocol. Permits multiple sub-channels, on different channels, to be grouped together in a fashion similar to traditional SNA Transmission Groups (TGs) to increase channel throughput and provide high-availability. Initially used to support HPR but now used with TCP/IP.

Multiple-Subsystem Scope:  DB2 classes with the subsystem ID as part of the RACF resource name.

Multiplexer:  A generic device (also known as a mux) that combines data from two or more devices, transmits the data as a single datastream over a high-speed communications medium, and disentangles (de-multiplexes) the data at the other end. See also Statistical multiplexer.

Multi-point:  Communications configuration in which a single primary node communicates with two or more secondary nodes (which cannot communicate with one another, except through the primary). Also known as multi-drop.

Multiprise:  Multiprise 2000 and 3000. The 2000 was a System/390 mid-range processor family, announced and delivered September 1996. Aimed primarily at the z/VM and VSE/ESA community, although it will also run z/OS, and available only as a packaged solution, under the Entry Server Offering label (which included various planning and maintenance services and support for the year 2000). Doesn’t support Parallel Sysplex. Replaced by the 3000 September 1999, which provided more performance for less money. The 3000 was replaced by models in the eserver zSeries 900 on October 3, 2000.

Multiprotocol Switched Services:  A set of Control Point functions that were added to IBM’s Networking BroadBand Services (NBBS), in August 1995, through the auspices of the Switched Virtual Networking (SVN) initiative. The MSS services embrace the notion of distributed routing, ATM2 LAN Emulation, Broadcast Management, and VLANs. MSS Services had been available through the IBM 8210 Nways MSS Server until it was withdrawn in September 2000.

Multisystem node:  See multisystem RRSF node.

Multisystem RRSF node:  An RRSF node with multiple z/OS system images that share the same RACF database.

MultiView:  A range of AIX products which provided access to a broad range of hosts. Renamed MultiView Mascot then withdrawn in May 1996.

MUMPS:  Massachusetts General Hospital Utility MultiProgramming System (now known as M Technology). Minicomputer operating system originally written for DEC kit, and widely used within the health sector. Has been implemented under z/VM as a 20+ user system. MUMPS/VM is a full implementation of the Micronetics standard MUMPS and was written jointly by Micronetics and IBM. MUMPS/VM was intended to provide a way of luring users from their non-IBM (mostly DEC) machines to IBM hardware, where it would have been easier for IBM to complete the conversion to the mainstream IBM world. Withdrawn February 1995.

MUSIC:  McGill University System Interactive Computing. Little-known z/VM software combining applications, bulletin boards, conferencing, text search, compiler interfaces, utilities, and lots more besides. IBM support ended May 1986.

MUX:  See Multiplexer.

MVPG/1:  MOVEPAGE Facility.

MVPG/2:  Enhanced MOVEPAGE Facility.

MVS:  Multiple Virtual Storage. In z/OS’s long history, MVS has the honor of being its name for the longest period: about two decades. Admittedly, it had many suffixes during those years: MVS/SP, MVS/370, MVS/XA and MVS/ESA. Many users believed that MVS stood for Man Versus System.

MVS/370:  The name for MVS/SP once MVS/XA was announced.

MVS/400:  Once rumored implementation of the Fort Knox concept of combining the mainframe and iSeries 400 architectures on a single box. See also MVS.

MVS/ASA:  Advanced Systems Architecture. Rumored top-end mainframe operating environment. Depending on which rumors you were listening to, it: (1) became OS/390; (2) became z/OS; or (3) it never happened.


MVS/CNAT:  MVS/Central Node Administration Tool. See CNAT1.

MVS/ESA:  MVS Enterprise System Architecture. Version of MVS, first introduced as MVS/SP Version 3 in February 1988. Replaced by/renamed as OS/390 late 1995.

MVS/ESA OpenEdition:  Version of MVS/ESA announced February 1993 with support for POSIX standards. Included about 1 million new lines of code which provide an API shell, utilities, and an extended user interface. Works with a hierarchical file system provided by DFSMS. The shell and utilities are based on Mortice Kerns’ InterOpen products. Independent specialists reckon it is over 80% open systems-compliant – more than most Unix systems. DCE2 support announced February 1994, and lots of application development tools in March 1995. Mid 1995 IBM started to stop referring to OpenEdition as a separate entity, as all the open features became a standard part of vanilla MVS/ESA. Under OS/390, it became Unix System Services, and has kept that name under z/OS. See also OpenEdition.

MVS/IS:  MVS/Integrated System. At one time a planned compact version of z/OS for the 9370. However, producing such a beast appeared to be an insoluble problem. See also VM/IS.

MVS/MS:  MVS Migration System. Automated aid for converting from VSE to z/OS originally developed by Sisro. Translates programs, converts JCL, transfers files, provides VSE services which don’t have z/OS equivalents, etc. Announced by IBM October 1986. Little used and withdrawn December 1997 to avoid checking it for Y2K compatibility.

MVS/OCCF:  Multiple Virtual Storage/Operator Communication Control Facility. A facility that helps network operators to control multiple z/OS systems from a central site by intercepting messages from the z/OS supervisor. Replaced by NetView January 1996.

MVS/SP:  MVS/System Product. For many years, a name for the z/OS operating system. More accurately, one of several names. MVS/SP Version 1 meant MVS/370, Version 2 meant MVS/XA and Version 3-5 meant MVS/ESA. Version numbers were often abbreviated, as in MVS/SP2 for MVS/SP Version 2.

MVS/XA:  MVS/Extended Architecture. Version of z/OS, which supported 31-bit addressing. Available only on the high-end 43xx, and 308x and later ranges. Replaced by MVS/ESA, then OS/390 and now z/OS. See also AMODE, MVS/370, MVS/SP.

MVS/XB:  Media name for the rumored successor to MVS/XA. Finally appeared as MVS/ESA.

MVS System Logger:  Despite two name changes (OS/390 and z/OS), the MVS System Logger is still the current name for this z/OS error logging feature.

MVT:  Multiprogramming with a Variable number of Tasks. A forerunner of MVS and z/OS (from a long, long time ago). Long since dead and buried.

Mwave:  Family of signal processing chips.

MWC:  Mirror Write Consistency. See Active MWC.