The CICS® intercommunication facilities enable you to implement many different types of distributed transaction processing. This section describes a few typical applications. The list is by no means complete, and further examples are presented in the other chapters of this topic of the book.
Multiregion operation makes it possible for two CICS regions to share selected system resources, and to present a "single-system" view to terminal operators. At the same time, each region can run independently of the other, and can be protected against errors in other regions. Various possible applications of MRO are described in Multiregion operation.
CICS intersystem communication, together with an SNA access method (ACF/VTAM) and network control (ACF/NCP/VS), allows resources to be distributed among and shared by different systems, which can be in the same or different physical locations.
Figure 1 shows some typical possibilities.
Many users have computer operations set up in each of the major geographical areas in which they operate. Each system has a database organized toward the activities of that area, with its own network of terminals able to inquire on or update the regional database. When requests from one region require data from another, without intersystem communication, manual procedures have to be used to handle such requests. The intersystem communication facilities allow these "out-of-town" requests to be automatically handled by providing file access to the database of the appropriate region.
Using CICS function shipping, application programs can be written to be independent of the actual location of the data, and able to run in any of the regional centers. An example of this type of application is the verification of credit against customer accounts.
Some users are organized by division, with separate systems, terminals, and databases for each division: for example, Engineering, Production, and Warehouse divisions. Connecting these divisions to each other and to the headquarters location improves access to programs and data, and thus can improve the coordination of the enterprise.
The applications and data can be hierarchically organized, with summary and central data at the headquarters site and detail data at plant sites. Alternatively, the applications and data can be distributed across the divisional locations, with planning and financial data and applications at the headquarters site, manufacturing data and applications at the plant site, and inventory data and applications at the distribution site. In either case, applications at any site can access data from any other site, as necessary, or request applications to be run at a remote site (containing the appropriate data) with the replies routed back to the requesting site when ready.