IBM mainframe
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SAS 8 on an IBM mainframe under 3270 emulation |
An
IBM mainframe is a large, high performance computer made by .
Mainframe computers traditionally are "expensive,"
[The acquisition price of one mainframe is higher than, say, one PC. However, that's a bit like saying the acquisition price of a train freight car is higher than the price of a bicycle basket. Both can move goods, but there the similarity ends, and the costs depend almost entirely on the tasks required of them. Mainframes reduce labor costs, software costs, and costs of outage, among other costs, because they are systems designed to achieve significant economies of scale.] individually physically large
[Nowadays, because mainframes consolidate scores or even hundreds of otherwise individual servers, they consume less electricity and occupy less space than equivalent workloads executing on individual servers. Most 21st century data centers require much more space for distributed servers than for mainframes.], and have high
transaction processing and
I/O performance, but are not as expensive and high performance
[In single computational task terms. Weather modeling, protein folding analysis, nuclear explosion simulation, digital cinematography, and structural engineering analysis are examples of computational problems better suited to supercomputers. Mainframes are optimized for business transaction processing and large online database management, among other tasks.] as
supercomputers.
Here are the different processors on an IBM Mainframe and their different functions
CP, Central Processor : Core, Operation system processor
IFL, Integrated Facility for Linux : dedicated for Linux and VM (Virtual Machine)
ICF, Integrated Coupling Facility : For sysplex (system complex = assembly of several system) operations
SAP : System Assist Processor : Processor unit dedicated to Input Output operations
zAAP : System z9 Application Assist Processor : Dedicated for Java workloads
zIIP : System z9 Integrated Information Processor, designed to run certain key database workloads
From
1952 into the late
1960s, IBM manufactured and marketed several large computer models, known as the
IBM 700/7000 series. The 700s were based on
vacuum tubes, while the later 7000s used
transistors. These machines established IBM's dominance in electronic data processing. IBM had two model categories: one (701, 704, 709, 7090, 7040) for engineering and scientific use, and one (702, 705, 7080, 7070, 7010) for commercial or data processing use. IBM initially sold its computers without any software, expecting customers to write their own; and programs were manually initiated, one at a time. This followed the model IBM had earlier established with their
unit record equipment. Later IBM provided compilers for the newly developed higher-level
programming languages
Fortran and
Cobol. The need to make the most efficient use of these multi-million dollar machines led to the introduction of simple
operating systems, or job monitors. The two categories, scientific and commercial, generally used common peripherals but had completely different
instruction sets, and there were incompatibilities even within each category. As software became more complex and important, the cost of supporting it on so many different designs became burdensome.
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 number "
360" suggested a "360
degree," or "all-around" computer system.
System/360 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).
[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.] 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.
[Hardware memory protection was provided to protect the operating system from the user programs (tasks) and the user tasks from each other.] The new machine also had a larger
address space than the older mainframes, 24 bits vs. a typical 18 bits. The System/360 later evolved into the
System/370, the
System/390, the
zSeries, and the
System z9.
Prior to System/360, IBM also sold computers smaller in scale, though still large and expensive by modern standards. These included:
*
IBM 650 (vacuum tube era, decimal architecture, business and scientific)
*
IBM RAMAC 305 (vacuum tube era, first computer with disk storage;
see: Early IBM disk storage)
*
IBM 1400 series (business data processing; very successful and many 1400 peripherals were used with the 360s)
*
IBM 1620 (decimal architecture, engineering, scientific, and education)
IBM had difficulty getting customers to upgrade from the smaller machines to the mainframes because so much software had to be rewritten. The 7010 was introduced in 1962 as a mainframe-sized 1410.The smaller models in the System/360 line (e.g. the 360/30) were intended to replace the 1400 series while providing an easier upgrade path to the larger 360s. A desk size machine with a different instruction set, the
IBM 1130, was released to address the 1620's niche. It was mostly programmed in Fortran, which was relatively easy to adapt to larger machines when necessary.
The second generation products were a mainstay of IBM's business and IBM continued to make them for several years after the introduction of the System/360. (Some
IBM 7094s remained in service into the 1980s.) To smooth the transition from second generation to the new line, IBM used the 360's
microprogramming capability to emulate the more popular older models. Thus 360/30s with this added cost feature could run 1401 programs and the larger 360/65s could run 7094 programs. To run old programs, the 360 had to be halted and restarted in emulation mode. Many customers kept using their old software and one of the features of the later System/370 was the ability to switch to emulation mode and back under operating system control.
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.
*
List of IBM products*
Amdahl Corporation*
IBM minicomputer*Prasad, Nallur (1994).
IBM Mainframes: Architecture and Design, 2nd ed. McGraw-Hill Osborne Media. ISBN 0070506914.
[Now dated. For details on the significant 64-bit architectural changes, refer to IBM technical publications (see z/Architecture).]*
Official IBM mainframe page (zSeries/z9)*
UnOfficial IBM mainframe User Group
