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Dec 14, 2021

IBM CICS (Customer Information Control System) is a family of mixed-language application servers that provide online transaction management and connectivity for applications on IBM mainframe systems under z/OS and z/VSE.

IBM mainframe transaction monitor
For other uses, see CICS (disambiguation).
Other names Customer Information Control System
Initial release July 8, 1969; 52 years ago (July 8, 1969)
Stable release
CICS Transaction Server V5.6 / June 12, 2020; 17 months ago (2020-06-12)[1]
Operating system z/OS, z/VSE
Platform IBM Z
Type Teleprocessing monitor
License Proprietary
Website www.ibm.com/it-infrastructure/z/cics

CICS family products are designed as middleware and support rapid, high-volume online transaction processing. A CICS transaction is a unit of processing initiated by a single request that may affect one or more objects.[2] This processing is usually interactive (screen-oriented), but background transactions are possible.

CICS Transaction Server (CICS TS) sits at the head of the CICS family and provides services that extend or replace the functions of the operating system. These services can be more efficient than the generalized operating system services and also simpler for programmers to use, particularly with respect to communication with diverse terminal devices.

Applications developed for CICS may be written in a variety of programming languages and use CICS-supplied language extensions to interact with resources such as files, database connections, terminals, or to invoke functions such as web services. CICS manages the entire transaction such that if for any reason a part of the transaction fails all recoverable changes can be backed out.

While CICS TS has its highest profile among large financial institutions, such as banks and insurance companies, many Fortune 500 companies and government entities are reported to run CICS. Other, smaller enterprises can also run CICS TS and other CICS family products. CICS can regularly be found behind the scenes in, for example, bank-teller applications, ATM systems, industrial production control systems, insurance applications, and many other types of interactive applications.

Recent CICS TS enhancements include new capabilities to improve the developer experience, including the choice of APIs, frameworks, editors, and build tools, while at the same time providing updates in the key areas of security, resilience, and management. In earlier, recent CICS TS releases, support was provided for Web services and Java, event processing, Atom feeds, and RESTful interfaces.

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CICS was preceded by an earlier, single-threaded transaction processing system, IBM MTCS. An ‘MTCS-CICS bridge’ was later developed to allow these transactions to execute under CICS with no change to the original application programs.

CICS was originally developed in the United States at an IBM Development Center in Des Plaines, Illinois, beginning in 1966 to address requirements from the public utility industry. The first CICS product was announced in 1968, named Public Utility Customer Information Control System, or PU-CICS. It became clear immediately that it had applicability to many other industries, so the Public Utility prefix was dropped with the introduction of the first release of the CICS Program Product on July 8, 1969, not long after IMSdatabase management system.

For the next few years, CICS was developed in Palo Alto and was considered a less important “smaller” product than IMS which IBM then considered more strategic. Customer pressure kept it alive, however. When IBM decided to end development of CICS in 1974 to concentrate on IMS, the CICS development responsibility was picked up by the IBM Hursley site in the United Kingdom, which had just ceased work on the PL/I compiler and so knew many of the same customers as CICS. The core of the development work continues in Hursley today alongside contributions from labs in India, China, Russia, Australia, and the United States.

CICS originally only supported a few IBM-brand devices like the 1965 IBM 2741 Selectric (golf ball) typewriter-based terminal. The 1964 IBM 2260 and 1972 IBM 3270video display terminals were widely used later.

In the early days of IBM mainframes, computer software was free  bundled at no extra charge with computer hardware. The OS/360 operating system and application support software like CICS were “open” to IBM customers long before the open-source software initiative. Corporations like Standard Oil of Indiana (Amoco) made major contributions to CICS.

The IBM Des Plaines team tried to add support for popular non-IBM terminals like the ASCIITeletype Model 33 ASR, but the small low-budget software development team could not afford the $100-per-month hardware to test it. IBM executives incorrectly felt that the future would be like the past, with batch processing using traditional punch cards.

IBM reluctantly provided only minimal funding when public utility companies, banks and credit-card companies demanded a cost-effective interactive system (similar to the 1965 IBM Airline Control Program used by the American Airlines Sabrecomputer reservation system) for high-speed data access-and-update to customer information for their telephone operators (without waiting for overnight batch processing punch card systems).

When CICS was delivered to Amoco with Teletype Model 33 ASR support, it caused the entire OS/360 operating system to crash (including non-CICS application programs). The majority of the CICS Terminal Control Program (TCP  the heart of CICS) and part of OS/360 had to be laboriously redesigned and rewritten by Amoco Production Company in Tulsa Oklahoma. It was then given back to IBM for free distribution to others.

In a few years,[when?] CICS generated over $60 billion in new hardware revenue for IBM, and became their most-successful mainframe software product.

In 1972, CICS was available in three versions  DOS-ENTRY (program number 5736-XX6) for DOS/360 machines with very limited memory, DOS-STANDARD (program number 5736-XX7), for DOS/360 machines with more memory, and OS-STANDARD V2 (program number 5734-XX7) for the larger machines which ran OS/360.[3]

In early 1970, a number of the original developers, including Ben Riggins (the principal architect of the early releases) relocated to California and continued CICS development at IBM’s Palo Alto Development Center. IBM executives did not recognize value in software as a revenue-generating product until after federal law required software unbundling. In 1980, IBM executives failed to heed Ben Riggins’ strong suggestions that IBM should provide their own EBCDIC-based operating system and integrated-circuit microprocessor chip for use in the IBM Personal Computer as a CICS intelligent terminal (instead of the incompatible Intel chip, and immature ASCII-based Microsoft 1980 DOS).

Because of the limited capacity of even large processors of that era every CICS installation was required to assemble the source code for all of the CICS system modules after completing a process similar to system generation (sysgen), called CICSGEN, to establish values for conditional assembly-language statements. This process allowed each customer to exclude support from CICS itself for any feature they did not intend to use, such as device support for terminal types not in use.

CICS owes its early popularity to its relatively efficient implementation when hardware was very expensive, its multi-threaded processing architecture, its relative simplicity for developing terminal-based real-time transaction applications, and many open-source customer contributions, including both debugging and feature enhancement.

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