Mainframes (often colloquially referred to as Big Iron) are computers used mainly by large organizations for critical applications, typically bulk data processing such as census, industry and consumer statistics, ERP, and financial transaction processing. Big iron, as the hacker 's dictionary the Jargon File defines it "refers to large expensive ultra-fast computers A computer is a Machine that manipulates data according to a list of instructions. A census is the procedure of acquiring information about every member of a given population Enterprise resource planning ( ERP) is the planning of how business resources (materials employees customers etc For other meanings see the disambiguation page at Transaction.
The term probably originated from the early mainframes, as they were housed in enormous, room-sized metal boxes or frames.  Later the term was used to distinguish high-end commercial machines from less powerful units which were often contained in smaller packages.
Today in practice, the term usually refers to computers compatible with the IBM System/360 line, first introduced in 1965. The IBM System/360 ( S/360) is a Mainframe computer system family announced by IBM on April 7, 1964. (IBM System z10 is the latest incarnation. IBM System z10 is the latest line of IBM mainframes. It was announced on February 26 2008 and represents the first model powered by the z10 quad core ) Otherwise, large systems that are not based on the System/360 are referred to as either "servers" or "supercomputers". A server is a Computer dedicated to providing one or more services over a computer network typically through a request-response routine A supercomputer is a Computer that is at the frontline of processing capacity particularly speed of calculation (at the time of its introduction However, "server", "supercomputer" and "mainframe" are not synonymous (see client-server). The client-server Software architecture model distinguishes client systems from server systems which communicate over a Computer network
Some non-System/360-compatible systems derived from or compatible with older (pre-Web) server technology may also be considered mainframes. These include the Burroughs large systems, the UNIVAC 1100/2200 series systems, and the pre-System/360 IBM 700/7000 series. The Burroughs large systems were the largest of three series of Burroughs Corporation mainframe computers The UNIVAC 1100/2200 series is a series of compatible 36-bit computer systems beginning with the UNIVAC 1107 in 1962, initially made by Sperry Rand The IBM 700/7000 series was a series of large scale ( mainframe) Computer systems made by IBM through Most large-scale computer system architectures were firmly established in the 1960s and most large computers were based on architecture established during that era up until the advent of Web servers in the 1990s. (Interestingly, the first Web server running anywhere outside Switzerland ran on an IBM mainframe at Stanford University as early as 1990. Year 1990 ( MCMXC) was a Common year starting on Monday (link displays the 1990 Gregorian calendar) See History of the World Wide Web for details. The World Wide Web (" WWW " or simply the " Web " is a global Information medium which users can read and write via Computers )
There were several minicomputer operating systems and architectures that arose in the 1970s and 1980s, but minicomputers are generally not considered mainframes. A minicomputer (colloquially mini) is a class of multi-user Computers that lies in the middle range of the computing spectrum in between the largest Multi-user (UNIX arose as a minicomputer operating system; Unix has scaled up over the years to acquire some mainframe characteristics. Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer )
Many defining characteristics of "mainframe" were established in the 1960s, but those characteristics continue to expand and evolve to the present day.
Modern mainframe computers have abilities not so much defined by their single task computational speed (usually defined as MIPS — Millions of Instructions Per Second) as by their redundant internal engineering and resulting high reliability and security, extensive input-output facilities, strict backward compatibility for older software, and high utilization rates to support massive throughput. In Technology, especially Computing (irrespective of platform a product is said to be backward compatible when it is able to take the place of an older product These machines often run for years without interruption, with repairs and hardware upgrades taking place during normal operation. Software upgrades are only non-disruptive when Parallel Sysplex is in place, with true workload sharing, so one system can take over another's application, while it is being refreshed. In computing a Parallel Sysplex is a cluster of IBM mainframes acting together in a single system image usually with Z/OS. More recently, there are several IBM mainframe installations that have delivered over a decade of continuous business service as of 2007, with hardware upgrades not interrupting service. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Mainframes are defined by high availability, one of the main reasons for their longevity, as they are used in applications where downtime would be costly or catastrophic. The term Reliability, Availability and Serviceability (RAS) is a defining characteristic of mainframe computers. Reliability, Availability and Serviceability are Computer hardware engineering terms But, as with anything else, proper planning (and implementation) is required to exploit these features.
In the 1960s, most mainframes had no interactive interface. They accepted sets of punch cards, paper tape, and/or magnetic tape and operated solely in batch mode to support back office functions, such as customer billing. Batch processing is execution of a series of programs (" jobs quot on a Computer without human interaction A back office is a part of most Corporations where tasks dedicated to running the company itself take place Teletype devices were also common, at least for system operators. A teleprinter ( By the early 1970s, many mainframes acquired interactive user interfaces and operated as timesharing computers, supporting hundreds or thousands of users simultaneously along with batch processing. Users gained access through specialized terminals or, later, from personal computers equipped with terminal emulation software. A computer terminal is an electronic or electromechanical hardware device that is used for entering data into and displaying data from a Computer or a Computing A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated A terminal emulator, terminal application, term, or tty for short is a program that emulates a "dumb" video terminal within some other Many mainframes supported graphical terminals (and terminal emulation) by the 1980s (if not earlier). Nowadays most mainframes have partially or entirely phased out classic user terminal access in favor of Web user interfaces.
Historically mainframes acquired their name in part because of their substantial size and requirements for specialized heating, ventilating, air conditioning (HVAC), and electrical power. HVAC (pronounced either "H-V-A-C" or occasionally " H-vak " is an Initialism or Acronym that stands for " Heating Those requirements ended by the mid-1990s, with CMOS mainframe designs replacing the older bipolar technology. Complementary metal–oxide–semiconductor ( CMOS) (pronounced "see-moss" siːmɔːs ˈsiːmɒs is a major class of Integrated circuits CMOS technology A bipolar (junction transistor ( BJT) is a type of Transistor. In fact, in a major reversal, IBM touts the mainframe's ability to reduce data center energy costs for power and cooling and reduced physical space requirements compared to server farms. A server farm or server cluster is a collection of Computer servers usually maintained by an enterprise to accomplish server needs far beyond the capability 
Nearly all mainframes have the ability to run (or host) multiple operating systems and thereby operate not as a single computer but as a number of virtual machines. In Computer science, a virtual machine (VM is a Software implementation of a machine (computer that executes programs like a real machine In this role, a single mainframe can replace dozens or even hundreds of smaller servers, reducing management and administrative costs while providing greatly improved scalability and reliability. A server is a Computer dedicated to providing one or more services over a computer network typically through a request-response routine In Telecommunications and Software engineering, scalability is a desirable property of a system a network or a process which indicates its ability to either
Mainframes can add or hot swap system capacity non disruptively and granularly. Hot swapping and hot plugging are terms used to separately describe the functions of replacing system components hot swapping describes changing components like fans and Modern mainframes, notably the IBM zSeries, System z9 and System z10 servers, offer three levels of virtualization: logical partitions (LPARs, via the PR/SM facility), virtual machines (via the z/VM operating system), and through its operating systems (notably z/OS with its key-protected address spaces and sophisticated goal-oriented workload scheduling, but also Linux, Solaris and Java). IBM System z, or earlier IBM eServer zSeries, is a brand name designated by IBM to all its Mainframe computers In 2000 IBM rebranded the existing IBM System z9 is a line of IBM mainframes. It was announced on July 25 2005 and the first models IBM System z10 is the latest line of IBM mainframes. It was announced on February 26 2008 and represents the first model powered by the z10 quad core In Computing, a logical partition, commonly called an LPAR, is a subset of computer's hardware resources virtualized as a separate computer See also VM (operating system z/VM is the current version in IBM's VM family of Virtual machine Operating systems. z/OS is a 64-bit Operating system for Mainframe computers, created by IBM. Linux (commonly pronounced ˈlɪnəks Solaris is a Unix -based Operating system introduced by Sun Microsystems in 1992 as the successor to SunOS. This virtualization is so thorough, so well established, and so reliable that most IBM mainframe customers run no more than two machines: one in their primary data center, and one in their backup data center—fully active, partially active, or on standby—in case there is a catastrophe affecting the first building. Disaster recovery is the process policies and procedures of restoring operations critical to the resumption of business including regaining access to data (records hardware software All test, development, training, and production workload for all applications and all databases can run on a single machine, except for extremely large demands where the capacity of one machine might be limiting. Such a two mainframe installation can support continuous business service, avoiding both planned and unplanned outages.
Mainframes are designed to handle very high volume input and output (I/O) and emphasize throughput computing. Since the mid-1960s, mainframe designs have included several subsidiary computers (called channels or peripheral processors) which manage the I/O devices, leaving the CPU free to deal only with high-speed memory. The IBM System/360 ( S/360) is a Mainframe computer system family announced by IBM on April 7, 1964. The CDC 6600 was a Mainframe computer from Control Data Corporation, first delivered in 1964. It is common in mainframe shops to deal with massive databases and files. A Computer Database is a structured collection of records or data that is stored in a computer system Giga-record or tera-record files are not unusual.  Compared to a typical PC, mainframes commonly have hundreds to thousands of times as much data storage online, and can access it much faster. Computer data storage, often called storage or memory, refers to Computer components devices and recording media that retain digital
Mainframe return on investment (ROI), like any other computing platform, is dependent on its ability to scale, support mixed workloads, reduce labor costs, deliver uninterrupted service for critical business applications, and several other risk-adjusted cost factors. In Finance, rate of return ( ROR) also known as return on investment ( ROI) rate of profit or sometimes just return, is Some argue that the modern mainframe is not cost-effective. Hewlett-Packard and Dell unsurprisingly take that view at least at times, and so do a few independent analysts. The multinational technology company Dell Inc develops manufactures sells and supports Personal computers and other computer-related products Sun Microsystems used to take that view but, beginning in mid-2007, started promoting its new partnership with IBM, including probable support for the company's OpenSolaris operating system running on IBM mainframes. Sun Microsystems Inc ( is a multinational vendor of Computers computer components Computer software, and Information technology services OpenSolaris is an Open source project created by Sun Microsystems to build a developer community around Solaris Operating System technology The general consensus (held by Gartner and other independent analysts) is that the modern mainframe often has unique value and superior cost-effectiveness, especially for large scale enterprise computing. Gartner, Inc ( is an information technology research and advisory firm headquartered in Stamford, Connecticut. In fact, Hewlett-Packard also continues to manufacture its own mainframe (arguably), the NonStop system originally created by Tandem. NonStop servers are a line of Fault-tolerant computer systems, optimized for transaction processing and providing an extreme level of availability and data integrity Logical partitioning is now found in many UNIX-based servers, and many vendors are promoting virtualization technologies, in many ways validating the mainframe's design accomplishments. Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer
Mainframes also have unique execution integrity characteristics for fault tolerant computing. In Engineering, Fault-tolerant design, also known as fail-safe design, is a design that enables a system to continue operation possibly at a reduced level (also known z900 and z990 and System z9 and z10 servers execute each instruction twice, compare results, and shift workloads "in flight" to functioning processors, including spares, without any impact to applications or users. This feature, also found in HP's NonStop systems, is known as lock-stepping, because both processors take their "steps" (i. NonStop servers are a line of Fault-tolerant computer systems, optimized for transaction processing and providing an extreme level of availability and data integrity e. instructions) together. Not all applications absolutely need the assured integrity that these systems provide, but many do, such as financial transaction processing.
Despite these differences, the IBM mainframe, in particular, is still a general purpose business computer in terms of its support for a wide variety of popular operating systems, middleware, and applications. Middleware is computer Software that connects Software components or applications
As of early 2006, IBM mainframes dominate the mainframe market at well over 90% market share. IBM mainframes, though perceived as synonymous with Mainframe computers in general due to their marketshare are now technically and specifically IBM 's line of business Market share, in Strategic management and Marketing, is the percentage or proportion of the total available Market or Market segment that is Unisys manufactures ClearPath mainframes, based on earlier Sperry and Burroughs product lines. Unisys Corporation ( based in Blue Bell, Pennsylvania, United States, and incorporated in Delaware, is a global provider of information technology Sperry Corporation (1910-1986 was a major American equipment and Electronics company whose existence spanned more than seven decades of the twentieth century The Burroughs Corporation began in 1886 as the American Arithmometer Company in St Hitachi co-developed the zSeries z800 with IBM to share expenses. () is a Multinational corporation specializing in high-technology and services headquartered in Marunouchi Itchome Chiyoda, Tokyo, Japan. IBM System z, or earlier IBM eServer zSeries, is a brand name designated by IBM to all its Mainframe computers In 2000 IBM rebranded the existing Hewlett-Packard sells its unique NonStop systems, which it acquired with Tandem Computers. NonStop servers are a line of Fault-tolerant computer systems, optimized for transaction processing and providing an extreme level of availability and data integrity Tandem Computers was an early manufacturer of Fault-tolerant computer systems, marketed to the growing number of Transaction processing customers who used them for Groupe Bull's DPS, Fujitsu-Siemens BS2000, and Fujitsu-ICL VME mainframes are still available in Europe. Groupe Bull (also known as Bull Information Systems or simply Bull) is a French owned Computer company headquartered in Les Clayes-sous-Bois is a Japanese company specializing in Semiconductors Computers ( Supercomputers Personal computers, servers, Telecommunications BS2000 (officially renamed BS2000/OSD in 1992 is the mainframe Operating system platform of Fujitsu Siemens Computers. This article is about the operating system VME may also refer to the VMEbus computer bus Fujitsu, Hitachi, and NEC (the "JCMs") still maintain nominal mainframe hardware businesses in their home Japanese market. is a Japanese multinational IT company headquartered in Minato Tokyo, Japan.
The amount of vendor investment in mainframe development varies with marketshare. Unisys, HP, Groupe Bull, Fujitsu, Hitachi, and NEC now rely primarily on commodity Intel CPUs rather than custom processors in order to reduce development expenses, and they have also cut back their mainframe software development. In contrast, IBM has its own large research and development organization designing new, homegrown CPUs, including mainframe processors, and IBM is rapidly expanding its software business, including its mainframe software portfolio, to seek additional profits.  
Platform Solutions Inc. , which was spun off former plug compatible mainframe vendor Amdahl Corp. Amdahl Corporation was founded by Dr Gene Amdahl, a former IBM employee in 1970 and specializes in IBM mainframe -compatible computer products in January 1999,PSI history. Retrieved on 2008-04-24. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1479 BC - Thutmose III ascends to the throne of Egypt, although power effectively shifts to Hatshepsut (according to markets Itanium-based servers compatible with IBM System z. Itanium is the brand name for 64-bit Intel Microprocessors that implement the Intel Itanium architecture (formerly called IA-64) IBM System z, or earlier IBM eServer zSeries, is a brand name designated by IBM to all its Mainframe computers In 2000 IBM rebranded the existing PSI and IBM are engaged in a series of lawsuits. IBM alleges that PSI violated its patents and refuses to license its software on PSI systems, while PSI alleges that IBM is violating anti-trust laws. A patent is a set of Exclusive rights granted by a State to an inventor or his assignee for a fixed period of time in exchange for a disclosure of an In October of 2007, PSI has additionally filed a complaint with the EU concerning IBM anti-competitive behavior in the European mainframe market. 
Several manufacturers produced mainframe computers from the late 1950s through the 1970s. The 1950s Decade refers to the years of 1950 to 1959 inclusive This article is about the Decade 1970-1979 For the Year 1970 see 1970. The group of manufacturers was first known as "IBM and the Seven Dwarfs": IBM, Burroughs, UNIVAC, NCR, Control Data, Honeywell, General Electric and RCA. The group of Mainframe computer competitors to IBM in the 1970s became known as the BUNCH: Burroughs, UNIVAC, NCR, Control Data International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology The Burroughs Corporation began in 1886 as the American Arithmometer Company in St UNIVAC serves as the catch-all name for the American manufacturers of the lines of mainframe computers by that name which through mergers and acquisitions underwent NCR Corporation ( is a technology company specializing in products for the retail and financial sectors Control Data Corporation (CDC, was one of the pioneering Supercomputer firms Honeywell ( is a major American multinational conglomerate company that produces a variety of consumer products engineering services and aerospace systems RCA Corporation, founded as Radio Corporation of America, was an electronics company in existence from 1919 to 1986 Later, shrinking, it was referred to as IBM and the BUNCH. The group of Mainframe computer competitors to IBM in the 1970s became known as the BUNCH: Burroughs, UNIVAC, NCR, Control Data IBM's dominance grew out of their 700/7000 series and, later, the development of the 360 series mainframes. The IBM 700/7000 series was a series of large scale ( mainframe) Computer systems made by IBM through The IBM System/360 ( S/360) is a Mainframe computer system family announced by IBM on April 7, 1964. The latter architecture has continued to evolve into their current zSeries/z9 mainframes which, along with the then Burroughs and now Unisys MCP-based mainframes, are among the few mainframe architectures still extant that can trace their roots to this early period. Unisys Corporation ( based in Blue Bell, Pennsylvania, United States, and incorporated in Delaware, is a global provider of information technology The Burroughs large systems were the largest of three series of Burroughs Corporation mainframe computers That said, while they can still run 24-bit System/360 code, the 64-bit zSeries and System z9 CMOS servers have nothing physically in common with the older systems. Notable manufacturers outside the USA were Siemens and Telefunken in Germany, ICL in the United Kingdom, and Fujitsu, Hitachi, Oki, and NEC in Japan. Telefunken is a German radio and television company founded in 1903 in Berlin, as a joint venture of two large companies Siemens & Halske (S & H and Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. International Computers Ltd, or ICL, was a large British Computer hardware, Computer software and Computer services company that operated from The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located is a Japanese company specializing in Semiconductors Computers ( Supercomputers Personal computers, servers, Telecommunications () is a Multinational corporation specializing in high-technology and services headquartered in Marunouchi Itchome Chiyoda, Tokyo, Japan. is a Japanese multinational IT company headquartered in Minato Tokyo, Japan. For a topic outline on this subject see List of basic Japan topics. The Soviet Union and Warsaw Pact countries manufactured close copies of IBM mainframes during the Cold War; the Strela is an example of an independently designed Soviet computer. The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 The Warsaw Pact (see Nomenclature) was an organization of Communist states in Central and Eastern Europe. Cold War is the state of conflict tension and competition that existed between the United States and the Soviet Union (USSR and their respective allies from the Strela computer (ЭВМ "Стрела" English "Arrow" was the first Mainframe computer manufactured serially in the Soviet Union since 1953
Shrinking demand and tough competition caused a shakeout in the market in the early 1980s — RCA sold out to UNIVAC and GE also left; Honeywell was bought out by Bull; UNIVAC became a division of Sperry, which later merged with Burroughs to form Unisys Corporation in 1986. Groupe Bull (also known as Bull Information Systems or simply Bull) is a French owned Computer company headquartered in Les Clayes-sous-Bois Sperry Corporation (1910-1986 was a major American equipment and Electronics company whose existence spanned more than seven decades of the twentieth century Unisys Corporation ( based in Blue Bell, Pennsylvania, United States, and incorporated in Delaware, is a global provider of information technology Year 1986 ( MCMLXXXVI) was a Common year starting on Wednesday (link displays 1986 Gregorian calendar) In 1991, AT&T briefly owned NCR. Year 1991 ( MCMXCI) was a Common year starting on Tuesday (link will display full calendar of the Gregorian Calendar. Before proposing a merge request please see Talk and see if the merger you propose has recently been made and During the same period, companies found that servers based on microcomputer designs could be deployed at a fraction of the acquisition price and offer local users much greater control over their own systems given the IT policies and practices at that time. Terminals used for interacting with mainframe systems were gradually replaced by personal computers. A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated Consequently, demand plummeted and new mainframe installations were restricted mainly to financial services and government. In the early 1990s, there was a consensus among industry analysts that the mainframe was a dying market as mainframe platforms were increasingly replaced by personal computer networks.
That trend started to turn around in the late 1990s as corporations found new uses for their existing mainframes and as the price of data networking collapsed in most parts of the world. The growth of e-business also dramatically increased the number of back-end transactions processed by mainframe software as well as the size and throughput of databases. Electronic Business, commonly referred to as " eBusiness " or " e-Business " may be defined as the utilisation of information and communication Another factor currently increasing mainframe use is the development of the Linux operating system, which can run on many mainframe systems, typically in virtual machines. Linux on System z is the collective term for the Linux operating system compiled to run on IBM mainframes especially System z machines Linux allows users to take advantage of open source software combined with mainframe hardware RAS. Open source is a development methodology which offers practical accessibility to a product's source (goods and knowledge Rapid expansion and development in emerging markets, particularly China, is also spurring major mainframe investments to solve exceptionally difficult computing problems, e. The term emerging markets is used to describe a nation's social or business activity in the process of rapid Industrialization. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National g. providing unified, extremely high volume online transaction processing databases for 1 billion consumers across multiple industries (banking, insurance, credit reporting, government services, etc. )
The distinction between supercomputers and mainframes is not a hard and fast one, but supercomputers generally focus on problems which are limited by calculation speed while mainframes focus on problems which are limited by input/output and reliability ("throughput computing") and on solving multiple business problems concurrently (mixed workload). A supercomputer is a Computer that is at the frontline of processing capacity particularly speed of calculation (at the time of its introduction The differences and similarities include:
There has been some blurring of the term "mainframe," with some PC and server vendors referring to their systems as "mainframes" or "mainframe-like. " This is not widely accepted and the market generally recognizes that mainframes are genuinely and demonstrably different.
The CPU speed of mainframes has historically been measured in millions of instructions per second (MIPS). Instructions per second (IPS is a measure of a Computer 's processor speed MIPS have been used as an oversimplified comparative rating of the speed and capacity of mainframes. The smallest System z9 IBM mainframes today run at about 26 MIPS and the largest System z10 at about 30,657 MIPS — a 1 to 1179 performance capacity ratio. IBM's Parallel Sysplex technology can join up to 32 of these systems, making them behave like a single, logical computing facility of as much as about 981,024 MIPS. In computing a Parallel Sysplex is a cluster of IBM mainframes acting together in a single system image usually with Z/OS. 
The MIPS measurement has long been known to be misleading and has often been parodied as "Meaningless Indicator of Processor Speed. " The complex CPU architectures of modern mainframes have reduced the relevance of MIPS ratings to the actual number of instructions executed. Likewise, the modern "balanced performance" system designs focus both on CPU power and on I/O capacity, and virtualization capabilities make comparative measurements even more difficult. See benchmark (computing) for a brief discussion of the difficulties in benchmarking such systems. This article is about the use of benchmarks in computing for other uses see Benchmark. IBM has long published a set of LSPR (Large System Performance Reference) ratio tables for mainframes that take into account different types of workloads and are a more representative measurement. However, these comparisons are not available for non-IBM systems. It takes a fair amount of work (and maybe guesswork) for users to determine what type of workload they have and then apply only the LSPR values most relevant to them. Also, IBM does not measure all workloads on all possible configurations, so some estimates are inaccurate. Current processors can have up to 64 CPU's, but LSPR has not measured any over 32. This is not negligence. Rather, it is a cost item.
To give some idea of real world experience, it is typical for a single mainframe CPU to execute the equivalent of 50, 100, or even more distributed processors' worth of business activity, depending on the workloads. Merely counting processors to compare server platforms is extremely perilous.