CICS

Customer Information Control System ( CICS ) is a transaction monitor from IBM.

CICS is under the / 390 mainframe operating systems z / OS (MVS ) and VSE, and available in modified form as Encina extension, AIX, HP -UX, Solaris, and Windows Server.

Pronunciation

Depending on the country the abbreviation CICS is pronounced differently:

  • In Germany, mostly as Zick: Without CICS runs nothing!.
  • In the UK, more like kicks
  • In the U.S., kicks and see eye see ess are common.

Application development under CICS

There are traditionally popular mainframe programming languages ​​COBOL, C, C , PL / I and assembler supports, for some years now Java.

The application API for non- OO languages ​​consists of EXEC CICS ..... commands that are translated by a preprocessor into the host language. Java programmers are appropriate CICS classes.

In contrast to the coding of the EXEC CICS IMS blocks in all the standard HOST languages ​​(see above ) are identical. An EXEC CICS ASSIGN ..... looks in COBOL, C, C , PL / I and Assembler from identical.

CICS programs to interact with a user or another application. For the programmers are a variety of mechanisms and functions. For example, the following features are important for classic, screen-oriented applications

  • SEND MAP / RECEIVE MAP to display information and collection of user input
  • RETURN TRANSID to terminate the CICS task under specification of follow-up transaction after user input
  • TS QUEUE READ / WRITE TS QUEUE is terminated for temporary storage of program data during the CICS task and waits for input or to communicate with other applications.

Transactions in CICS

A CICS transaction consists of one or more unit of work ( UOW ). A unit of work is what understood in the literature under a transaction and is associated with the term ACID ( atomicity, consistency, isolation and durability ). The obsolete term Logical Unit of Work (LUW ) is still used as a synonym for unit of work.

Each CICS transaction running under a pre-defined four-digit transaction code. This transaction code sets out inter alia the name of the program that receives the execution control to the start of the transaction.

With the start of a transaction unit of work begins with the command EXEC CICS SYNCPOINT the current unit of work is ended ( commited ) and started a new unit of work. The transaction ends with EXEC CICS RETURN and will also end the current unit of work with SYNCPOINT. A CICS transaction is created traditionally

  • By entering a transaction code to a terminal (or in the terminal emulator on a PC )
  • From a CICS application out with START TRANSID () or RETURN TRANSID () ( especially in " pseudoconversational " transactions )
  • CICS internal: eg trigger on TD queue.
  • From another CICS Transaction Routing with or Distributed Program Link ( DPL).

CICS transactions can be "outside" of programs started by:

  • EXCI call from z / OS ( MVS Multiple Virtual Storage ), for example, TSO (Time Sharing Option) or batch processing.
  • In the MVS operator console or software consoles (for example, TSO, NetView ).
  • Eci call not MVS platforms (Unix, Windows, OS / 2)
  • Using standard protocols: TCP / IP sockets and APPC ( Advanced Program to Program Communications )
  • IIOP ( Internet Inter- ORB Protocol) for CORBA applications and Enterprise JavaBeans
  • Via HTTP / HTTPS can use CICS as a Web server

History of CICS

According to Bob Yelavich Ben Riggins is the father of CICS.

Many myths surround the prefix of CICS messages DFH. Bob Yelavich indicates that this combination of letters from IBM was assigned plain and it is not an abbreviation (see IMS and the prefix DFS), say some sources, however, the first CICS would be a product of a local electricity provider with the company abbreviation DFH been, and was later bought by IBM.

The true story of CICS can no longer be clarified, it is clear only that CICS has surfaced in the early 1970s and originally was not from IBM.

In the GDR in the late 1980s there was a data communication system called DACS, which under OS / ES - SVS, the East German clone of the IBM operating system OS/VS2 ran. The prefix of the DAKS messages was DKS, the semantics of the messages was identical (eg Control is being givenName to DAKS ). How far it has spread and applied, is unknown, but it lost its importance because most data centers their software and hardware brought to the Economic and Monetary Union in the GDR to the western standard.

Future of CICS

CICS is used worldwide in many major companies. Since CICS is under ongoing development and support the latest versions of both popular programming languages ​​such as C / C and Java, as well as the corresponding interfaces have to the Internet ( CICS Web Support ) and web services, one can assume that the market for CICS next, at least in the years will remain relatively stable. In New customer market segment, CICS must maintain in the future against a growing competition with systems based on low-cost servers or hosts with high availability.

z/OS VSE (operating system) IBM AIX Assembly language#Assembler Time-Sharing Option Network socket East Germany Host (network)
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