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 5 or 6 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 5 or 6 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.

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