The storage tuning user exit is called when Language Environment is initializing its region level resources. On CICS®, this call occurs only once during CICS startup. On non-CICS, this call only occurs once when Language Environment is initialized to run the first program. At this point the storage tuning user exit is passed a user word. The storage tuning user exit can acquire any resources it needs. For example it may allocate memory for an incore table and put the address of the table in the user word.