Using the FREEZE|NOFREEZE option

For an LLA-managed library, use the FREEZE|NOFREEZE option to indicate whether the system is to search the LLA-cached or DASD copy of a library directory. With FREEZE|NOFREEZE, which you code in the CSVLLAxx member, you specify on a library-by-library basis which directory copy the system is to search, as follows:

If you specify FREEZE, the system uses the copy of the directory that is maintained in the LLA address space (the library is "frozen").
If you specify NOFREEZE, the system searches the directory that resides in DASD storage.

The system always treats libraries in the LNKLST concatenation as frozen. Therefore, you need only specify the FREEZE option for non-LNKLST libraries, or for LNKLST libraries that are referenced through TASKLIBs, STEPLIBs, or JOBLIBs.

When an LLA-managed library is frozen, the following is true:

Users of the library always receive versions of the library's modules that are pointed to by the LLA-cached directory.
Users do not see any updates to the library until LLA is refreshed. If a user does multiple linkedits to a member in a FREEZE data set, the base for each subsequent linkedit does not include the previous linkedits; the base is the LLA version of the member.
If the version of a requested module matches the version of the module in VLF, the users receive the module from VLF. Otherwise, users receive the module from DASD.

To take full advantage of LLA's elimination of I/O for directory search, specify FREEZE for as many read-only or infrequently updated libraries as appropriate.

Having NOFREEZE in effect for an LLA-managed library means that your installation does not eliminate I/O while searching the library's directory. However, LLA can still improve performance when the system fetches load modules from the VLF data space instead of DASD storage.

Table 1 summarizes the affects of the FREEZE|NOFREEZE option on directory search and module fetch.

Table 1. FREEZE|NOFREEZE processing
Action	FREEZE or NOFREEZE	LNKLST Libraries Accessed From LNKLST	LNKLST Libraries Accessed Outside LNKLST	Other Non-LNKLST Libraries
Directory Search	FREEZE	LLA directory is used.	LLA directory is used.	LLA directory is used.
Directory Search	NOFREEZE	LLA directory is used.	DASD directory is used (I/O occurs)	DASD directory is used (I/O occurs)
Module Fetch	FREEZE	Requestor receives LLA version of module (from VLF data space or DASD).	Requestor receives LLA version of module (from VLF data space or DASD).	Requestor receives LLA version of module (from VLF data space or DASD).
Module Fetch	NOFREEZE	Requestor receives LLA version of module (from VLF data space or DASD).	Requestor receives most current version of module (from DASD or VLF data space, if staged).	Requestor receives most current version of module (from DASD or VLF data space, if staged).

You can change the FREEZE|NOFREEZE status of an LLA-managed library at any time through the MODIFY LLA command. Changing a library from NOFREEZE to FREEZE also causes a refresh of the directory information for that library (note that when a library is refreshed, all of its modules are destaged from the VLF data space, which will slow performance until new versions are staged).

For more information about specifying the FREEZE|NOFREEZE option, see the description of the CSVLLAxx member in z/OS MVS Initialization and Tuning Reference.