Library directory caching

The tableBASE library directory can now be cached in memory. This can dramatically reduce the time needed to open a large number of tables when a TSR is initially loaded.

In an in-house test, load time for 40,000 tables from a tableBASE library into a local TSR was reduced from 11 hours to 7 minutes. This was an extreme stress test; your results may vary.

Caching for a library is controlled by coding OPTCD=C on the DD statement for a library. This feature is not supported in a CICS region. The initial loading of a TSR may benefit from the use of the library directory caching feature, and subsequent refreshes may also benefit if more than one table from the library is being refreshed. However, if updates are being done to the library while the loading or refreshing is being performed, these benefits will be lost. It is also important to note that the library directory caching feature is enabled only at region initialization.

Caching has significant benefit when a library is accessed heavily by a region and other regions are not frequently updating the library. However, caching can have negative performance consequences when multiple regions are frequently updating the library directory.

This feature should provide equivalent or better results than LSR pooling. There is limited support for VSAM tableBASE libraries using LSR pools. For more information on using LSR pooling, refer to VSAM tableBASE libraries and LSR pools.