The Evolution of CICS

The Evolution of CICS: CICS - State of the Art (1991)

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 1991.

CICS faced challenges on all fronts in 1991. The rearchitected CICS/ESA Version 3 product was slowly being accepted by the user community, but there was concern for those accounts still holding back on CICS/VS 2.1.2. IBM introduced various incentives for accounts to begin their migration to the new product. To deal with the discontinuance of the macro level interface, a number of aids were being offered, such as the COBOL CICS Conversion Aid (CCCA), the DFHMSCAN utility and CICS' own Application Migration Aid.

CICS/MVS 2.1.2 was announced in February 1991 and shipped in March. CICS again reiterated that new enhancements would be built on the command level interface only and any future enhancements to CICS/MVS would only be with regard to coexistence or migration assistance. As it worked out, CICS/MVS 2.1.2 was the last release to support the macro level interface and BTAM. A number of customers remained on CICS/MVS 2.1.2 for quite some time and it wasn't until the late 1990s that the number became quite small.

New function delivered in CICS/MVS 2.1.2 only included improvements in LU6.2 switched line support, delivery of CICS publications in softcopy via CD-ROM and a new Application Programming Primer, with annotated examples written in COBOL. Source code for all the examples given in the primer were shipped with the product and could be used as self-study or the basis for in-house CICS programming education.

The Development Management System (DMS) for CICS came into being in the late 1970s and received considerable IBM marketing support that DMS be used as an application generator for CICS. In the early 1980s there was marketing emphasis on the newly introduced IBM 4300 systems and DMS was a key element of those related marketing programs.

DMS has some success but its ultimate downfall was with regard to data integrity. Early in DMS' life cycle its generated code attempted to handle enqueue/dequeue for resources being updated, however this did not mesh with CICS' own data integrity mechanisms. To compound matters, DMS was written using CICS' macro level interface, now being discontinued by the CICS/ESA Version 3 product. In June 1991 DMS announced its Release 5 and delivered the new release in July 1991. DMS code now used the CICS command level interface but users were responsible for any exit programs they may have written using the macro level interface. Conversion to command level and dissatisfaction with DMS' method of insuring data integrity soon caused a downturn in DMS usage.

CICS had delivered its first release of Version 3 in 1990. In June 1991 CICS announced the availability of the 3.2.1 release. The new rearchitected product introduced many new features and considerable rework of its internal code. Experience and customer feedback with the initial 3.1 release helped CICS Development improve the product (e.g. storage management). New function was delivered in 3.2.1, such as support for Backup-While-Open (BWO), support for MVS/ESA's cross system coupling facility (XCF), online messages and codes (CMAC) and softcopy publications via CD-ROM.

The intent of BWO was to enable customer to backup their VSAM files while CICS continued to run, thereby eliminating a CICS scheduled outage just to back up files. Translation? Higher availability. Support of XCF improved communications between CICS-connected regions in an MRO configuration, meant better performance and terminal response time. Online M&C and softcopy publications were considered user productivity enhancements.

The CICS VSAM Recovery product (CICSVR) followed suit by announcing its support of BWO and added new support for batch backout. CICSVR would continue to evolve and provide increasing support for VSAM recovery, well into the new century.

The 1990s was a decade during which the industry was focusing on high availability for online systems. MVS and CICS cooperated with various enhancements such as the new automated operator capabilities and CICS' support offered by its Extended Recovery Facility (XRF). Enhancements such as these improved startup, shutdown and recovery scenarios.

In September of 1991, CICS announced a Statement of Direction (SoD) that it would provide a CICS capability for the AS/400. There were approximately 250,000 AS/400s installed in the early 1900s and if for no other reason, it appeared that there was a potential market for CICS among those systems.

The Information Technology (IT) industry and its attendant trade press and consulting community were paying increased attention to keys concerns of the times. In response, IBM issued a major announcement documenting its strategy. In September 1991 IBM published its "Commitment to the Open Enterprise". The announcement reiterated CICS and IMS as being strategic and delivering support of high availability, client/server and open systems. A key part of this announcement was IBM's restatement and goals for System Application Architecture (SAA) and its common interfaces such as Common User Access (CUA) and Common Programming Interface for Communications (CPIC).

The Screen Definition Facility (SDF II) product also paid heed to the industry pressure and announced its support of SAA, support of application generators such as the Cross System Product (CSP), MVS/XA and more. SDF II was primarily concerned with the generation of CICS Basic Mapping Support (BMS) maps.

As if IBM's announcement to support open systems was not enough, IBM also issued an announcement in September 1991 to draw attention to "IBM Transaction Processing Solutions for Continuous Availability". Again, CICS was a major part of that announcement. The announcement described improved IBM ES/9000 hardware, Automated Operator Control for CICS (AOC/CICS), CICS XRF, and a new capability. MVS had announced its intent to support the new hardware for Subsystem Storage Protection (SSSP). CICS issued a Statement of Direction (SoD) that CICS/ESA Version 3 would support the new capability.

1991 was a challenging year for CICS. Delivery of the 3.2.1 release incorporated lessons learned from the initial introduction of the rearchitected product. Industry pressures in multiple interest areas were being responded to. CICS worked with its related products in an attempt to delivered best-of-breed support for high volume, high response, online transaction processing systems.