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.
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. 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.
History
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. IBM's Customer Information Control System (CICS) was first developed in conjunction with Michigan Bell in 1966. Ben Riggins was an IBM systems engineer at Virginia Electric Power Co. when he came up with the idea for the online system.
CICS was originally developed in the United States out of the 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 IMS database 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 IBM labs in India and the United States.
Early evolution 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 3270 video 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 ASCII Teletype 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 Sabre computer 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.
Customer Information Control System (CICS) stands as one of IBM's most commercially successful software products. In the years following its introduction, the transaction processing monitor became a cornerstone of IBM’s mainframe strategy, ultimately generating over $60 billion in associated hardware revenue. By facilitating high-volume, reliable transaction processing, CICS solidified its position as a critical component of the enterprise computing landscape and remains a primary driver of the IBM mainframe ecosystem.
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.
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 relatively immature MS-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.
Z notation Part of CICS was formalized using the Z notation in the 1980s and 1990s in collaboration with the Oxford University Computing Laboratory, led Tony Hoare. Ib Holm Sørensen led the Transaction Processing Project itself at Oxford University, from its inception in 1982 (later renamed the CICS ProjectFitzgerald, J. S. (October 2006). Perspectives on Formal Methods in the Last 25 years. Technical Report Series. Vol. CS-TR-983. UK: Newcastle University.), in collaboration with IBM Hursley.Hayes, Ian (1993). "Preface to the first edition". Specification Case Studies. International Series in Computer Science (2nd ed.). Prentice Hall. . This work won a Queen's Award for Technological Achievement in 1992."Prof Jim Woodcock, FREng" . UK: University of York. As part of the CICS project, Sørensen extended Edsger Dijkstra's Guarded Command Language by allowing the use of Z-schema notation as abstract commands.Hayes, Ian J.; King, Steve (2021). "11.9 Industry Influence on Research". In Jones, Cliff B.; Misra, Jayadev (eds.). Theories of Programming: The Life and Works of Tony Hoare. Association for Computing Machinery. pp. 266–267. .
CICS as a distributed file server In 1986, IBM announced CICS support for the record-oriented file services defined by Distributed Data Management Architecture (DDM). This enabled programs on remote, network-connected computers to create, manage, and access files that had previously been available only within the CICS/MVS and CICS/VSE transaction processing environments.
In newer versions of CICS, support for DDM has been removed. Support for the DDM component of CICS z/OS was discontinued at the end of 2003, and was removed from CICS for z/OS in version 5.2 onward. In CICS TS for z/VSE, support for DDM was stabilised at V1.1.1 level, with an announced intention to discontinue it in a future release. In CICS for z/VSE 2.1 onward, CICS/DDM is not supported.
CICS and the World Wide Web CICS Transaction Server first introduced a native HTTP interface in version 1.2, together with a Web Bridge technology for wrapping green-screen terminal-based programs with an HTML facade. CICS Web and Document APIs were enhanced in CICS TS V1.3 to enable web-aware applications to be written to interact more effectively with web browsers.
CICS TS versions 2.1 through 2.3 focused on introducing CORBA and EJB technologies to CICS, offering new ways to integrate CICS assets into distributed application component models. These technologies relied on hosting Java applications in CICS. The Java hosting environment saw numerous improvements over many releases. A multi-threaded JVM resource called the JVMSERVER was introduced during the CICS TS version 4.1 release, this was further enhanced to use 64-bit JVM technology in version 5.1. Version 5.1 also saw the introduction of the WebSphere Liberty profile web-container. Ultimately WebSphere Liberty was fully embedded into CICS Transaction Server in version 5.3. Numerous web facing technologies could be hosted in CICS using Java, this ultimately resulted in the removal of the native CORBA and EJB technologies.
CICS TS V3.1 added a native implementation of the SOAP and WSDL technologies for CICS, together with client side HTTP APIs for outbound communication. These twin technologies enabled easier integration of CICS components with other Enterprise applications, and saw widespread adoption. Tools were included for taking traditional CICS programs written in languages such as COBOL, and converting them into WSDL defined Web Services, with little or no program changes. This technology saw regular enhancements over successive releases of CICS.
CICS TS V4.1 and V4.2 saw further enhancements to web connectivity, including a native implementation of the Atom publishing protocol.