The Evolution of CICS

The Evolution of CICS: CICS/VS - Managing Evolution (1975)

During the period 1974-1976, responsibility for the CICS products was being transferred from the IBM Programming Center in Palo Alto, CA, to the IBM Laboratory at Hursley, England. The CICS product family, including CICS/OS/VS and CICS/DOS/VS were experiencing success in the marketplace. Competition had to be dealt with, inside and outside the IBM company. CICS customers wanted a DL/I capability with CICS, and vendors were offering online transaction processing products as an alternative to CICS.

New technology was emerging, rapidly, and CICS was expected to respond. Customers initially attracted to CICS had serious requirements in order to make realtime, online systems something they could commit to. So, while the transfer of development responsibilities were in process, new technologies had to be incorporated, and CICS also found itself trying to quickly demonstrate responsiveness to major customer requirements. 1975 was not a quiet time.

Both the CICS/OS/VS and CICS/DOS/VS products made headway in 1975. With the introduction of CICS for virtual systems, CICS responded by delivering a succession of releases (1.1, 1.0.1 and 1.1.1) to incorporate new technology and respond to user requirements.

The initial 1968-1969 CICS offerings offered access to standard access method files such as ISAM and BDAM. By 1975, VSAM had become available, and users were very much interested in having a DL/I data base capability with CICS, so support for DL/I DOS/VS and IMS/VS DB was added to the CICS DOS and OS products respectively. A more critical requirement however was that in order to make online processing viable, more data integrity would be required. The CICS/VS products added support for backout as a part of emergency restart for transactions that were in flight at the time of a system failure. This backout included VSAM, ISAM, BDAM and DL/I. CICS also added backout as part of emergency restart for CICS' Temporary Storage Auxiliary Storage facilities as well.

The early 1970s introduced new technology for the IBM 3270 Information Display System and virtual storage management provided by the operating systems. VTAM and SNA became the new technologies for networking, and CICS was expected to embrace all of these technologies. CICS introduced its support for the 3270 family of products, support of virtual storage too. Most CICS users in 1975 were using BTAM for terminal support, so the CICS support of VTAM and SNA evolved slowly. CICS felt the pressure from users to improve BTAM support while at the same time, some users, and especially IBM, were expecting support for the new network devices and the new VTAM access method.

CICS responded with support for the new VTAM/SNA devices such as the 3600 Financial Communication System and other programmable terminals. In 1976, CICS would announce CICS/VS 1.2 and the major content of that release would be more extensive support for VTAM/SNA and the newer terminals. CICS Development invested early in support of the new access method and terminals beginning in 1975.

Customer interest in having a DL/I capability for use with CICS became very clear by 1975. DLI DOS/VS had no online capability so it was natural to look to CICS for such support. Some IBM employees expected OS customers interested in a DL/I capability would choose IMS/VS as their terminal and data base management system, however in spite of IBM marketing attempts, CICS users held firm, expecting a DL/I capability for use with CICS and not be required to choose and/or migrate to an IMS/VS DB/DC platform. Their patience was rewarded, however slowly, with CICS being able to improve its DL/I capability over a period of years. In 1975, the measure of success was that CICS/OS/VS was at least able to have multi-threaded use of DL/I (with a CICS adaptation of IMS/VS DB at the time).

Support for TCAM networks was a bit of a problem for CICS. TCAM was widely recommended and sold during the late 1960s and into the 1970s. In the mid-1960's, IBM invested heavily in message switching hardware and software, the strategy being to replace antiquated torn tape and teletype systems of an earlier age. The late 1960s and early 1970s however demonstrated the more important customer requirement for online transaction processing. So, whereas a number of customers began their online processing with TCAM-based systems, a portion of the marketplace wanted a TCAM capability in conjunction with a CICS type of transaction processing system.

The original CICS product (pre-VS) offered support for TCAM. That is, a terminal which was part of a TCAM network could cause units of work to be routed to a CICS system, executed and results returned to the TCAM-supported terminal. The intial CICS support met with reasonable success, but with the introduction of virtual storage systems and moreover, the introduction of VTAM and SNA, IBM decided to drop the CICS support of TCAM. This was not favorably received by CICS TCAM customers and the support was reinstated in CICS/VS during the mid-1970s.

Odd as it may seem, a popular piece of CICS evolution was in the introduction of support for using the operating system console as a CICS terminal. Prior to such support being added to the CICS OS and DOS products, a Field Developed Program (FDP) demonstrated that there was considerable customer interest in such a tool. The interest was not so much for production applications but probably more so as a system programmer tool for checking on CICS applications or systems status. In any case, CICS support for the operating system console as a CICS terminal was added to the product in response to the popular customer requirement.

In the early years, the installation of CICS required a full system generation of the product, meaning assembly and link editing of all CICS-provided software. Over time, CICS simplified system generation, eventually eliminating it altogether by providing object code only and a fully generated system. But, in the 1975 time period, this aspect of CICS was still evolving. The products at that time reduced the amount of printing caused by system generation.

The CICS systems of 1975 added a number of other enhancements, some of which have evolved to comprehensive facilities of this day. The initial CICS products had a trace facility and the CICS/VS products improved this by expanding it to include auxiliary trace. CICS statistical information was now recorded at various time intervals giving the user better insight as to CICS' behavior and performance. During the CICS/VS evolution, CICS Development observed customer usage of virtual storage and added improvements to CICS storage management to better meet the needs of the new environment. For example, CICS added parameters to such things as anticipatory paging.

1975 was not a dull year for CICS. The product was being moved from Palo Alto to Hursley. Virtual storage and the 3270 were new. Customers wanted more from CICS. CICS Development was committed not to let the high acceptance of CICS to slow down.