CICS coupling facility data tables is designed to provide rapid sharing of working data within a sysplex, with update integrity. The data is held in a table that is similar in many ways to a shared user-maintained data table, and the API used to store and retrieve the data is based on the file control API used for user-maintained data tables.
Coupling facility data tables are held in coupling facility structures, and access to a coupling facility data table is through a named server. Coupling facility data tables allows you to have related groups of coupling facility data tables stored in separate pools. For example, you might want to have one pool for production and another for test.
Within each MVS™ image, there must be one CFDT server for each CFDT pool accessed by CICS® regions in the MVS image. Coupling facility data table pools are defined as a list structure in the coupling facility resource management (CFRM) policy. The pool name, which is used to form the server name with the prefix DFHCF., is specified in the start-up JCL for the server.
Coupling facility data table pools can be used almost continuously and permanently. CICS provides utility commands that you can use to minimize the impact of maintenance.
Figure 51 illustrates a Parallel Sysplex® with three CICS AORs linked to the coupling facility data table servers.
The server must be authorized to access the coupling facility list structure in which the data table pool is defined; XES checks this. The server must also be authorized to act as a data table server; AXM checks this. For information on how to define the necessary authorizations see the CICS RACF® Security Guide.
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