Data table sharing environment

The environment for sharing a data table is the same as for any file accessed in non-RLS mode: one CICS® region owns the data table--this region is known as a file-owning region (FOR). Any other region that uses the data table is known as an application-owning region (AOR). In the FOR, the file is known as a local file and, in the AOR, the file is known as a remote file.

In the context of shared data tables, the FOR is also known as a server and the AOR is also known as a requester.

The same region can be both an FOR for some data tables and an AOR for others.

For information about these intercommunication concepts, see the CICS Intercommunication Guide.

Shared data tables support uses cross-region sharing wherever possible to provide access to data tables that are in the same MVS™ image as the requesting CICS region. This means that most read accesses within the same MVS image are satisfied by cross-region sharing using shared data tables services. If cross-region sharing is not possible for the request, function shipping is used. This means that update requests from CICS regions within the same MVS image and all requests from CICS regions in different MVS images use function shipping. Application programming for a CICS-maintained data table and Application programming for a user-maintained data table tell you when commands are satisfied by either cross-region sharing or function shipping.

Note:
Similarly, XCF/MRO does not provide shared data table access between CICS regions in different MVS images.

Although shared data tables support is primarily intended for sharing data within an MVS image, the support may be extended to a sysplex environment for applications that require only read access to a shared user-maintained data table or can operate with data that might not be up-to-date. The data table must be replicated across each MVS region in the sysplex, and updated periodically. See Using shared data tables support in a sysplex.

Related concepts
Application programming for a CICS-maintained data table
Application programming for a user-maintained data table
Using shared data tables support in a sysplex
Introduction to shared data tables
The concept of shared data tables
Description of data tables
Source data set for data tables
Data space for data tables
Global user exits for data tables
Benefits of shared data tables
Shared data table services and remote file access
How a data table is shared
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