Developed in Scotland, Telecommunications Access Method (TCAM) came along in 1971 with the birth of TSO. It supported asynchronous messaging, as with MQ. TCAM 3.0 added in reusable disk message queues for recovery soon thereafter, as with MQ. A high-level PL/I program could be used to access TRANSIENT datasets (dynamic message queues). Reading a message from a transient dataset resulted in that message is removed from the queue, as with a non-browse READ with MQ. With the advent of computers, IBM saw an opportunity to apply new technology to the need for message switching. In the early 1960s, IBM marketed computer-like devices, such as the 7740 and 7750 message switching systems.
The IBM System/360 was announced in April 1964 and with it came communication access methods such as BTAM and QTAM (Basic and Queued Telecommunications Access Methods). In the late 1960s, still another communication access method became available and it was known as TCAM, the Telecommunications Access Method. TCAM offered its users a more advanced form of message switching or message routing. TCAM was widely accepted, especially in the financial and brokerage industries.
In the late 1960s, transaction management systems came into being, each trying to achieve a leadership position in the industry. Within IBM, CICS and IMS were chosen as strategic products to address the need for transaction management. Within both CICS and IMS, each had its version of message switching, IMS being a front-end queued system and CICS having its Transient Data facility as the possible basis for message switching.
CICS established itself as a popular transaction management system in the 1968-1971 timeframe, those users who had adopted TCAM for its message handling capabilities, now wanted a combined use of TCAM with CICS. In December 1971, IBM announced CICS support of TCAM as part of the CICS/OS-Standard product, to be delivered in December 1972. For interested customers, this enabled them to use TCAM for its message handling strengths and also have TCAM-connected terminals or computers interface with CICS online applications.
In January 1973, TCAM continued to be supported by CICS/OS-Standard Version 2.3. However, TCAM support was omitted from the initial release of CICS/VS, announced in February 1973 and delivered in June 1974. Needless to say, many CICS-TCAM customers were not happy with that product direction.
With considerable pressure from CICS-TCAM customers, the CICS support of TCAM was reinstated in the CICS/VS 1.1 product, as of September 1974. In addition to the previous DCB support, with this reinstatement of TCAM support, CICS began to support TCAM access via VTAM, also known as the ACB support. CICS TCAM ACB support was discontinued as of the CICS/ESA Version 3 product in 1990.
In 1992, IBM announced a new product family called WebSphere MQ. WebSphere MQ was to be the extension of TCAM functionality from IBM-only systems to all other platforms. WebSphere MQ had an architecture which enabled heterogeneous systems to communicate with each other (e.g. IBM, HP, Sun, Tandem, etc). WebSphere MQ can be used with CICS systems to send and receive data to/from any other MQ-eligible system. WebSphere MQ can be used to initiate work in a CICS system or a CICS transaction can initiate work in another CICS or non-CICS system.
WebSphere MQ now supports 80 different environments and has become the leading message switching/routing product in the industry.
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