The Evolution of CICS

The Evolution of CICS: CICS - State of the Art (1973)

Preface: With each new version and release of the Customer Information Control System (CICS), the product introduced support of new or improved technologies. When reviewing the evolution of CICS, one has to remember the date of the product enhancement, and then consider the nature of the enhancement and why it was important at the time. This article examines the CICS "State of the Art" relevant in 1973.

The wide customer acceptance of CICS in the period 1968-1972 created considerable focus on the product family. If left to its own, CICS Development would most likely have enhanced the product in a modest, progressive manner. However, the popularity of the product brought increased expectations for the product, both from customers and prospects but also from IBM itself.

Virtual storage systems were introduced in the 1972-1973 timeframe. The operating systems were making significant changes to support the new technology. Systems with a given amount of real storage were now to appear as having considerably more storage by way of a paging scheme which kept an image of a region or partition's storage on direct access storage devices (DASD) and "paged" into real storage only those segments of storage being referenced at the moment.

In February 1973, CICS announced support of virtual storage systems, plus a significant number of product enhancements not directly related to the new storage environments. CICS/OS was now to become CICS/OS/VS and the two CICS/DOS products (CICS DOS Standard and CICS DOS Entry) would be merged into a new product, CICS/DOS/VS. Both new products were scheduled for availability in February 1974.

Early CICS users wanted increased system reliability if they were to implement real time, online transaction processing systems. In the area of improved reliability, CICS/VS now provided dynamic storage verification, attempting to detect storage overruns that might otherwise cause system failures. CICS/VS also added support for a variety of exits (STAE, SPIE and STXIT) at which the user could participate in the handling of abnormal conditions. Still further, CICS/VS now included the option of controlled shutdown and warm restart, enabling the user to restart CICS with the status it had at shutdown.

CICS support of data management now included support of the new VSAM file organizations and access method. VSAM data could be organized as keyed, indexed, direct, sequential or in a relative record format. A DL/I interface was added to both the CICS/OS/VS and CICS/DOS/VS products, providing the use of IMS/VS and DL/I DOS/VS data bases, respectively. These enhancements were driven by user expectations and requirements for support of the newer technologies.

CICS Temporary Storage was enhanced to provide both sequential and direct retrieval. Transaction initiation now allowed one to four character transaction IDs, as well as initiation via 3270 PA and/or PF keys. Journal Control was added to the product to provide for recording of user and/or CICS system data.

User application programming was further enhanced by CICS Built-In Functions and extended Basic Mapping Support (BMS)(message routing, terminal paging). CICS operations was enhanced by the addition of master terminal commands to dynamically alter the run time environment, as well as the use of a new CICS-provided message switching transaction.

Consistent with IBM's announcement for the concentration of its software development efforts for data base/data communication (DB/DC) products made in 1971, CICS/VS provided migration assistance for FASTER users. In addition to migration documentation, IBM issued Statements of Direction (SoD) that software would be produced enabling users to execute FASTER applications as part of CICS.

The announcement of the CICS/VS products did several things for IBM and the CICS user community. It demonstrated CICS' continued functional growth, responsiveness to user requirements and expectatons, and incorporation of new technologies, without affecting the user's existing application investments. This was the CICS State of the Art in 1973.