Storage tuning user exit

When Language Environment® is used in transaction processing environments where Language Environment enclaves are constantly being initialized and terminated, such as CICS® online and IMS/TM message processing regions, tuning the Language Environment storage options can improve the performance of the transactions. By tuning the Language Environment storage options, it can reduce the time spent doing system GETMAINs and it can reduce the time spent initializing Language Environment stack and heap increments.

The Language Environment storage tuning user exit is provided to help manage the task of setting Language Environment storage option values that provide the best performance in transaction processing environments where Language Environment enclaves are constantly being initialized and terminated. The Language Environment storage tuning user exit can be used to manage the Language Environment storage values for your main programs without having to statically link-edit the storage values with your load modules.

Note: When running on CICS, the Language Environment automatic storage tuning for CICS may provide the storage tuning function you need without having to use the Language Environment storage tuning user exit. See Language Environment automatic storage tuning for CICS for a discussion of Automatic Storage Tuning (AUTOTUNE) for CICS.

The Language Environment storage tuning user exit provides a programming interface that allows you to:

Collect Language Environment storage tuning information without having to run with the RPTSTG option.
Set the Language Environment runtime options STACK, LIBSTACK, HEAP, ANYHEAP, and BELOWHEAP for each Language Environment enclave.
Note: Vendor Heap Manager (VHM) is not handled by the Language Environment storage tuning user exit.
Alter the behavior of Language Environment automatic storage tuning for CICS.

The storage tuning exit can be used when running on CICS or when running on non-CICS with library routine retention. The name of the exit is as follows:

CEECSTX for CICS
CEEBSTX for non-CICS

The storage tuning exit is loaded when Language Environment loads its other runtime load modules. On CICS, the storage tuning exit is loaded during CICS startup. On non-CICS with LRR, the storage tuning exit is loaded when Language Environment is initialized to run the first program. If the load of the storage tuning exit is not successful, Language Environment does not issue a message. It also does not attempt to call the storage tuning exit.

The storage tuning user exit is called at certain times during Language Environment processing.

Region initialization
Region termination
Enclave initialization
Enclave termination
New load module (CICS only)