Data tables management exits XDTRD, XDTAD, and XDTLC

Data tables management exits apply to both CICS shared data tables and CICS coupling facility data tables.

XDTRD and XDTAD allow you to control the selection of records for inclusion in a data table, XDTRD being used to make such selections during loading, and XDTAD being invoked when records are subsequently added to a loaded data table (or to a CFDT that did not require loading). XDTRD also allows the contents of records that are included in a user-maintained table, or a coupling facility data table, to be modified before they are added.

For CICS® shared data tables, XDTLC enables you to take action based on the fact that a data table has completed loading, which might be to end some restrictions that you have decided to place on access to the data table during loading, or to cater for an unsuccessful completion of the loading.

For a coupling facility data table, XDTLC allows your global user exit program to decide whether to accept an unsuccessfully loaded coupling facility data table. If the user exit program decides to accept the table, it remains open and available for access, but CICS does not mark it as loading completed. This is also the default action if no XDTLC exit is enabled. This means that application programs continue to receive the LOADING condition for any records that are beyond the key range of records successfully loaded into the table. This ensures that application programs are aware that not all the expected data is available. It also allows you to retry the load, when the cause of the failure has been corrected, by closing the file that initiated the load and reopening it. Alternatively, you could open another load-capable file that refers to the same data table. If your exit program decides to reject the table, it is closed and the records already loaded remain in the table. If the cause of the failure is corrected, a subsequent open for the data table allows the load to complete. XDTLC is not invoked for a coupling facility data table that is not loaded from a source data set.

Note that a program invoked from any of these exit points must declare a DSECT defining the data tables user exit parameter list pointed to by field UEPDTPL. (Although UEPDTPL is defined by a DFHUEXIT call, the parameter list that it addresses is not.) To do this, your program can include the copybook DFHXDTDS, which defines the DT_UE_PLIST DSECT.

If any tables specify OPENTIME=STARTUP or are opened implicitly, you should provide a program list table post-initialization (PLTPI) program to activate the user exits. Otherwise, the data table might start loading before the exits can be enabled. For more details about PLTPI programs, see Writing initialization and shutdown programs.