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Revision as of 23:38, 28 August 2005 by Rewster (talk | contribs)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)An IBM mainframe is a large, high-performance computer made by International Business Machines (IBM). Mainframe computers traditionally are expensive, physically large, and have high transaction processing and I/O performance, but are not as expensive and high-performance as supercomputers.
Description
From 1950 to 1965, IBM and several other companies manufactured numerous computer models, most of which were incompatible with each other. IBM had two model categories: one for commercial or data processing use, and one for engineering and scientific use. The two categories were largely incompatible with each other, and there were incompatibilities even within each category. All that changed with the announcement of the System/360 (S/360) in April, 1964. The System/360 was a single series of compatible models for both commercial and scientific use. The System/360 later evolved into the System/370, the System/390, the zSeries, and the System z9.
System/360 (suggesting a "360 degree", or "all-around" computer system) incorporated features which had previously been present on only either the commercial line (such as decimal arithmetic and byte addressing) or the technical line (such as floating point arithmetic).¹ The System/360 was also the first computer in wide use to include dedicated hardware provisions for the use of operating systems. Among these were supervisor and application mode programs and instructions, as well as built-in memory protection facilities.²
Notable pre-System/360 IBM mainframes included:
- IBM 650 (business/data processing)
- IBM 704 (science/engineering)
- IBM 1401 (business/data processing)
- IBM 7090 (science/engineering)
Operating systems
The primary operating systems in use on IBM mainframes include z/OS (which followed MVS and OS/390), z/VM (previously VM/CMS), z/VSE, z/TPF, and Linux on zSeries. A few systems still run MUSIC/SP, another operating system. Previous operating systems for the System/360 family and its successors included OS/360 (with PCP, MFT, and MVT), BOS, TOS, DOS, and SVS. There are software-based emulators for the System/370, System/390, zSeries, and System z9 hardware, including FLEX-ES and the freely available Hercules emulator which runs under Linux and Microsoft Windows. The original OS/360 and early MVS and VM/CMS versions have been released for free use.
Middleware
IBM mainframes run all the major enterprise transaction processing environments and databases, including CICS, IMS, WebSphere Application Server, DB2, and Oracle. In many cases these software subsystems can run on more than one mainframe operating system.
See also
References
- Prasad, Nallur, IBM Mainframes: Architecture and Design, 2nd ed., 1994. McGraw-Hill Osborne Media, ISBN 0070506914.³
External links
Footnotes
¹ Some of the arithmetic units and addressing features were optional on some models of the System/360. However, models were upward compatible and most were also downward compatible.
² Hardware memory protection was provided to protect the operating system from the user programs (tasks) and the user tasks from each other.
³ Now dated. For details on the significant 64-bit architectural changes, refer to IBM technical publications. (See z/Architecture.)