Implementation of LLA/VLF to Control Load Module Fetching

The LLA (Library Lookaside) function of MVS/ESA manages both Linklist and non-Linklist libraries. Therefore, it is not necessary to place the IOA LOAD library in the Linklist in order to benefit from LLA. Without VLF (Virtual Lookaside Facility), the LLA only maintains direct pointers to modules residing in LLA controlled libraries. The combination of LLA and VLF improves module fetching by keeping modules in virtual storage. If VLF has a copy of a module that is controlled by LLA, no I/O operations are required to locate or retrieve the module from a PDS library.