Resource definition for CICS-maintained data tables

You use the DEFINE FILE command to define a file as a CICS®-maintained data table.

You can also change the definition of an existing file by the:

Only the base VSAM cluster can have a CICS-maintained data table based on it. Read requests via alternate index paths do not use the data table, but changes to the source data set via alternate index paths are reflected in the data table. Note that the source data set for a CICS-maintained data table cannot be open in RLS access mode. Thus the file definition must specify RLSACCESS(NO), as should any other files associated with the same base data set.

After a file that is defined as a CICS-maintained data table has been opened, any other non-UMT file (whether defined as a CMT or not) that names the same source data set in its definition automatically uses the same data table. If any of these other files are defined as CMTs, message DFHFC0937 is issued to the console when they are opened. This is not an error situation; the files are opened and use the existing data table whenever possible.

Either fixed-or variable-length record format can be specified for a CICS-maintained data table. The maximum record length that is supported by SDT is 32KB. This length exceeds that supported by CICS file management, which thus imposes the actual limit. See the topic dealing with lengths of areas passed to CICS commands in the CICS Application Programming Guide. The maximum number of records that is supported is 16 777 215.

For more information, see Resource definition for data tables.

VSAM SHAREOPTION

If the source data set is allocated with DISP=SHR, there is a risk that it could be updated by a region other than the FOR. If this happened, the data table would no longer match the source data set. To minimize this risk, the VSAM cross-region SHAREOPTION should be set to 1 or 2.

Regardless of the setting of DISP, a warning message is issued if the cross-region SHAREOPTION is 3 or 4, or if it is 2 but the CICS-maintained data table has read-only access (which means another region might be able to update the data set).

Data integrity

A file that uses a CICS-maintained data table can be defined as a recoverable resource. The source data set is recovered in the normal way after a system or transaction failure:

Automatic journaling is supported (in the same way as for any other file) for file operations that access the source data set. File operations that do not access the source data set are not journaled.

Related concepts
Resource definition for data tables
CICS-maintained data tables
Application programming for CICS-maintained data tables
Operations with CICS-maintained data tables
User-maintained data tables
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