The Evolution of CICS

The Evolution of CICS: CICS/OS/VS 1.8 - The release that never was (1987)

After designing and building CICS/OS/VS 1.7, CICS Development focused on the next release which was assumed to be CICS/OS/VS 1.8. A number of new line items were planned for the new release together with IBM announcing new directions for the CICS product.

Prevailing market conditions (competition) however caused CICS Development to revise their release plans. Tandem and Stratus were agressively marketing their 'high availability' offerings to the point that IBM and CICS had to take notice. IBM had delivered a Field Developed Program (FDP) called Peer Address Spaces (PAS) which enabled the CICS user to distribute the workload over multiple CICS address spaces, offering an element of high availability should a primary address fail. PAS was installed by some customers however it was not widely used.

A new direction for CICS (CICS/ESA) would have to wait. CICS/MVS Version 2 was announced on February 17, 1987 and was initially scheduled for availability in 4Q87. Release 2.1 eventually was made available on June 2, 1988. The thrust of CICS/MVS 2.1 was high availability and this goal was built around a new CICS facility called Extended Recovery Facility (XRF).

By configurating active and alternate CICS regions, and using the new CICS/MVS XRF facilities, CICS enabled the user to detect system failures and initiate an automatic transfer of the active workload to an alternate CICS region, on the same or different machine. Remote VTAM sessions were automatically moved to the newly activated CICS region. Data bases and datasets were also transferred to the new active CICS region. Provision was made for user participation in the takeover process, for instance to notify end-users of the event.

Follow-on releases CICS/MVS 2.1.1 and 2.1.2 were announced on June 20, 1989 and September 6, 1994 respectively. CICS/MVS 2.1.1 incorporated intervening maintenance and added support for selective VSAM subtasking, improvements in runaway task control, COMMAREA above the 16mb line and Data Tables support above 16mb.

CICS/MVS 2.1.2 was announced as the last release to support the CICS macro level application programming interface (API), although support for Assembler macro level programs continued with the introduction of CICS/ESA 3.1.

CICS/MVS 2.1.1 was also the last release of CICS to support BTAM and TCAM ACB usage. CICS/ESA Version 3 had no plans to support direct access to CICS control blocks, or the use of the EXEC CICS ADDRESS CSA command. Old master terminal commands and system initialization modules (SIMODs) would not be supported in CICS/ESA V3. All this meant was that CICS/MVS 2.1.2 was the last release to support certain functions, and the user had to factor this into his migration plans.

CICS/MVS 2.1.1 became available on June 30, 1989. End of currency (defect support) was announced for CICS/MVS 2.1 on June 20, 1989 to be effective on July 31, 1990. CICS/MVS 2.1.1 was announced for end of currency on February 19, 1991 to be effective on March 31, 1993. CICS/MVS 2.1.2 was announce for end of currency on September 6, 1994 to be effective on December 31, 1996.

During the lifespan of CICS/MVS and its three releases, many users began their migration to CICS/ESA. A number of users implemented CICS' XRF support, however users with high availability objectives were more interested in CICS' support of parallel systems which became available with the CICS/ESA product(s).

A number of users remained on CICS/MVS 2.1.2 for some time, citing either the macro level dependency or the belief that CICS/ESA did not provide sufficient motivation to justify migration. Although not recommended, macro level emulation through the use of third party vendor software has enabled some users to migrate to CICS/ESA and even CICS Transaction Server (CICS TS). As of 2003, the number of CICS customers still using CICS/MVS is very small.