The Evolution of CICS

The Evolution of CICS: CICS on UNIX - Good, bad or indifferent? (1992)

Beginning in the mid-1980s and throughout the 1990s, CICS began to "spread its wings" and provide support on a variety of hardware and operating system platforms. After establishing itself on the MVS and VSE platforms, CICS began to support the workstation with CICS OS/2. The next platform to be considered was that of UNIX, and for a variety of reasons.

A number of customers felt that the cost of computing on the mainframe was too expensive. This could have been a legitimate assessment in some cases but in other cases, it may have been a preference by IT management to provide services on the system they first experienced (a first love syndrome, some say). Whatever the justification, some CICS customers were considering migrating to a UNIX-based platform, with or without CICS.

Anticipating that some current or future CICS users may want to conduct transaction processing on a UNIX platform, CICS Development studied the market and finally committed to supporting UNIX-based systems, beginning with the announcement in September 1992 that CICS would offer support for the RISC System/6000 (RS/6000) and AIX operating system (IBM's UNIX-based operating system). The first release of CICS/6000 became available in December 1992.

In order to develop a CICS-like system on AIX some prerequisites were needed, either available from AIX itself or provided by some other means. For instance, UNIX does not offer a native VSAM capability. After some evaluation, CICS Development decided to base CICS/6000, in part, on third party software, Encina from Transarc Corporation, a Pittsburgh-based company.

Transarc was already marketing its Encina transaction monitor product for UNIX-based platforms and it contained certain functions CICS needed for an implementation on AIX. A VSAM capability for CICS was then built on the services of Encina software called the Structured File System (SFS). On one hand this seemed a compromise because AIX did not offer VSAM support, but given the emulation provided by SFS, there were actually some unexpected benefits. Among other things, SFS was already capable of providing both online and batch VSAM support, including concurrent read/write, which mainframe VSAM did not yet support.

Other Encina software that initially were prerequisites for the development of CICS/6000 were the Peer-to-Peer Executive and Gateway. The UNIX environment was largely TCP/IP-based and again this had to be dealt with in porting a CICS-like offering to the platform. CICS Development was able to adapt its AIX-based product to have terminal read/write facilities with a TCP network, and this included CICS' Intersystem Communications.

CICS/6000's first release became available in June 1993. The new product offered the UNIX-interested customer a full function CICS and its command level application programming interface. Programmers with CICS skills found application programming to be very similar in the new environment. The system programmer, however, had to deal with installing and administering CICS/6000 on a base quite different than the MVS or VSE system that he or she may have been familiar with.

In July 1993, CICS/6000 expanded its data management facilities by supporting Oracle, Informix and a commit/abort protocol known as XA. The significance of XA support was that a CICS/6000 system could now participate in distributed systems which may not be all IBM systems. If the remote systems also supported XA then two-phase commit would be possible with a mixture of data management systems (e.g. SFS and Oracle).

1994 brought continued growth for the CICS/6000 product, with performance improvements in the relatively new CICS implementation on AIX (UNIX) and now support of SNA Application Access for AIX. 3720s could appear to CICS/6000 as ASCII-based terminals or Telnet 3270s. That same year CICS Client support appeared.

In January 1995, IBM announced CICS/6000 1.2 and delivered the new release than same month. The CICS Client was extended, the internals of CICS/6000 now had less dependency on Encina-based software and new support for HACMP (High Availability Cluster Multi-Processing) was announced.

CICS/6000 expanded its support with the announcement of Version 2.1, to be delivered in late 1995. Two items were of particular significance in the new version. First of all, CICS/6000 now supported DB2 for AIX. The other important software was the introduction of CICS System Manager for AIX, a CICSPlex-like product, providing resource definition and administration facilities, and single point of control, single system image facilities. That is, the CICS SM facilities need not be on the same RS/6000 box as the CICS/6000 systems to be managed.

Having demonstrated the ability to adapt CICS to a UNIX platform (AIX), CICS Development took another step in December 1995 by delivering support for Siemens Nixdorf V2.1, another UNIX platform. As with the CICS/6000 product, CICS transaction management concepts and facilities were easily ported to this new environment.

In the 1996 timeframe, IBM began to package and title its software as "servers". Hence, what had been known as CICS/6000 was now being referred to as the Transaction Server for AIX. TS for AIX Version 4 also integrated a number of what previously had been separate software offerings. IBM had acquired the Transarc company at this time and with TS for AIX, it integrated into a single product, the Encina transaction monitoring facilities together with CICS/6000, CICS Client, CICS SM for AIX and the CICS Internet Gateway for AIX.

The new TS for AIX was a bold move and now offered the customer a wide choice of transaction processing capabilities. The customer could use a mixture of CICS and Encina in the same system. CICS offered its robust support of programming languages (COBOL, PL/I and C), data management including SFS and RDBMS, client/server support using CICS Client and its ECI/EPI interfaces, and a very rich menu of intersystem communications support(SNA and TCP, transaction routing, function shipping, distributed transaction processing, asynchronous transaction processing (START command), APPC and Distributed Computing Environment (DCE).

CICS support of UNIX platforms expanded again in 1996 with the announcement and delivery of support for still another UNIX-based system, Sun Solaris.

1998 was another milestone year for CICS being integrated into the new packaged and renamed TXSeries product offering. TXSeries announced support for (CICS on) AIX, HP-UX, Solaris and Windows NT. The AIX and Solaris support was delivered in April 1998 while the Windows NT and HP-UX support was delivered in June 1998. The TXSeries 4.2 product (as it was initially numbered) was further enhanced in December 1998 with the addition of support for the CICS Transaction Gateway (CTG) and the CICS Universal Client (CUC).

TXSeries was renamed in 2002 as TXSeries for Multiplatforms Version 5, partly to draw attention to the wide support for CICS transaction processing on UNIX-based platforms. Equally significant was the addition of support for Java application programs, Windows 2000 and the ability to interoperate with IBM's WebSphere software systems.

For the customer who wants to do transaction processing on UNIX-based platforms, whatever the reason, CICS has demonstrated its adaptability together with its robustness, performance, availability and reliability in these environments.