Tuning stack storage
For best performance, the initial stack segment should be large enough to satisfy all requests for stack storage. The Language Environment storage report generated by the RPTSTG(ON) option shows you how much stack storage is being used, the total number of segments allocated to the stack, and the recommended values for the STACK runtime option. An initial stack segment that is too large can waste storage and decrease overall system performance, especially under CICS® where storage is limited.
You can tune stack storage by using the Language Environment STACK and THREADSTACK runtime options. For more information, see Tuning stack storage in z/OS Language Environment Programming Guide for 64-bit Virtual Addressing Mode.
RPTSTG(ON) and the STORAGE runtime option can have a negative affect on the performance of your application, because as the application runs, statistics are kept on storage requests. Therefore, always use the IBM-supplied default setting RPTSTG(OFF) when running production jobs. Use RPTSTG(ON) and STORAGE only when debugging or tuning applications. For more information about RPTSTG and STORAGE, see STORAGE in z/OS Language Environment Programming Reference.