If you compress an LLA-managed library, LLA continues to provide the obsolete directory entries. For members that have been staged to the VLF data space, the system will operate successfully. If the member is not currently staged, however, the cached obsolete directory entry can be used to fetch the member at the old TTR location from DASD.

Because using obsolete directory entries can cause such problems as abends, breaches of system integrity, and system failures, use the following procedure to compress LLA-managed libraries:

1. Issue a MODIFY LLA,UPDATE=xx command, where the CSVLLAxx parmlib member includes a REMOVE statement identifying the library that needs to be compressed.
2. Compress the library
3. Issue a MODIFY LLA,UPDATE=xx command, where the CSVLLAxx parmlib member includes a LIBRARIES statement to return the compressed library to LLA management.

This procedure causes all members of that library to be discarded from the VLF data space. The members are then eligible to be staged again.