What are the considerations for using CA PDSMAN Library Space Reuse with LLA-managed libraries?

Document ID : KB000011359
Last Modified Date : 14/02/2018
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Introduction:

This document describes how PDSMAN Library Space Reuse automatically handles all considerations for using PDSMAN Library Space Reuse with LLA-managed libraries.

The IBM Library Look-Aside facility improves system performance by caching PDS and PDSE directory entries in virtual storage.

The PDSMAN Library Space Reuse facility offers a proactive solution to the problem of PDS out-of-space conditions and the related issues of unscheduled compressions, unnecessary compressions and PDS over-allocation.

Question:

What are the considerations for using CA PDSMAN Library Space Reuse with LLA-managed libraries?

Environment:
PDSMAN 7.7
Answer:

Library Space Reuse tracks and reuses the dead PDS space (or 'holes') that are created when PDS members are updated or deleted. Normally, these holes are available for immediate reuse. However, when a library is being managed by LLA in "Freeze" mode PDSMAN cannot reuse the holes until the entire LLA cache for the library has been refreshed.

PDSMAN automatically manages this situation using information provided by the PDSMAN LLA/Extensions facility. The LLA/Extensions provide information on which libraries are LLA managed, the mode (Freeze or NoFreeze) in which they are managed, and the last time a full LLA cache refresh was performed for the library.

The PDSMAN LLA Monitoring subtask, PDSMLMON, must be active in order to provide the necessary information to Library Space Reuse. It is a PDSMAN best practice that PDSMLMON be active whenever PDSMAN is running. You can check the status of the PDSMLMON subtask by issuing the F PDSMAN,LMONSTATUS address space command.

Reuse of free space holes can also be delayed using the $UPDATE Initialization Control Statement PSRTL parameter. It is not necessary to specify PSRTL for LLA-managed libraries. However, if PSRTL is specified, a hole will not be available for reuse until both the LLA cache has been refreshed and the PSRTL time limit has expired.

Freespace holes are available for immediate reuse when a library is being managed by LLA in "NoFreeze" mode.

 

Additional Information:

Additional information is available in the following documents:

  • The commands used to control and check the status of the LLA Monitoring subtask are described in the "Address Space Commands".