I thought I would discuss with my first June entry the possibly little known yet very useful CICS configuration option - RUWAPOOL - and how this can improve CICS storage usage with LE z/VSE applications.
This configuration parameter instructs CICS to pre-allocate storage for LE z/VSE CICS applications from a CICS managed storage pool - RUWA. This is the "Run-Unit Work Area". When ever a CICS transaction is executed that requires LE z/VSE run-time support CICS will provide to LE z/VSE two Rununit work area storage addresses. One for 24-bit related storage and another for 31-bit related storage. When LE z/VSE then starts initialisation processing it can utilise these storage areas immediately without the need to make specific calls to CICS for storage areas. This greatly improves initialisation processing time and since the storage is acquired from a CICS-managed storage pool this aids greatly with reducing fragmentation. With reduced fragmentation comes more available storage for more concurrent transaction processing.
Whenever an EXEC CICS LINK is performed to an LE application a similar problem can arise. Again by enabling the RUWAPOOL setting this will allow CICS to provide managed storage areas to LE z/VSE for initialisation processing that will help reduce the execution path way and enclave initialisation processing time.
With LE z/VSE 1.4.7 (z/VSE 4.3) this processing was further enhanced to include the storage area size required for BELOWHEAP use. Prior to LE z/VSE 1.4.7 there was always a subsequent EXEC CICS GETMAIN for the BELOWHEAP storage amount whenever an EXEC CICS LINK was performed to an application that required the use of BELOWHEAP. With LE z/VSE 1.4.7 and onwards, this BELOWHEAP value is now included in the storage size CICS will preallocate for LE z/VSE to use whenever an EXEC CICS LINK is performed to a LE application that requires BELOWHEAP storage. Thus eliminating the need to perform an "extra" EXEC CICS GETMAIN.
CICS RUWAPOOL Documentation reference : http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/DFHWT302/4.8.2