LLA-managed load libraries for performance

If you use Library Lookaside (LLA) to manage caching of COBOL load modules (PDS load libraries) and program objects (PDSE load libraries) for performance, COBOL V5 or V6 modules are not cached by LLA in the base versions of z/OS® because of the structure of their resulting program objects. IBM® has corrected this in the service stream via APAR OA45127. Alternatively, you can get a performance boost by enabling PDSE hyperspace caching, which helps the case of COBOL V5 or V6 program objects in load libraries that are managed by LLA.

One approach for loading large program objects is called page-fault driven loading. The initial load brings in only part of the program object; other parts of the program object might be brought in only when they are referenced, that is, when a page-fault occurs. For libraries that are managed by LLA, in some cases performance can be improved by avoiding page-fault driven loading. If you use the binder option FETCHOPT=(NOPACK,PRIME) for a program object, the system does not use page-fault driven loading. The default binder option of FETCHOPT=(NOPACK,NOPRIME) allows use of page-fault driven loading.

Note: When a program object resides in a library that is not LLA managed, the default binder option of FETCHOPT=(NOPACK,NOPRIME) might provide better performance.

Start of changeSee also Other product related factors that affect runtime performance, for considerations on using LLA when the program object contains RMODE 24 CSECTs.End of change