Library Lookaside (LLA)

  • It’s a program management z/OS component that keeps in Virtual Storage Directory entries from Load module libraries, thereby speeding up the fetch of a Load module.
  • LLA improves the performance of Load Module Directory searching on the system.
  • LLA can be a user of VLF facilities to keep copies of Load modules in VLF data spaces.
  • LLA manages Linklist libraries by default.
  • Code CSVLLAxx Parmlib member to include, modify or remove libraries.
  • Specify LLA with SUB=MSTR to prevent LLA from failing if JES2 fails.
  • Because LLA manages Linklist libraries by default, we only need to determine which non-Linklist libraries LLA is to manage.
  • If we don’t want LLA to manage particular Linklist libraries, we must explicitly remove such libraries from LLA management by using the CSVLLAxx Parmlib member.
  • When used with VLF, LLA reduces the I/O required to fetch Load modules from DASD.


SUB=MSTR indicates that the MASTER Subsystem will be the subsystem that will process the task.

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