Local Meta Cache Limit feature limits the size of a Local Meta Cache by removing it if it has not been accessed for a long time.

Of the definitions that SQL accesses, the main factors that make the Local Meta Cache bloat are tables and indexes. In addition, table column definitions are also maintained as a catalog cache.

For example, in a system where one long-lived connection is shared by various businesses, one connection (that is, backend process) will access many tables. If there are 3,000 such connections, and each connection accesses a table of 50,000, the total amount of memory consumed by the 3,000 backend processes may be a few terabytes.

In such a case, using this feature may reduce it to about several tens of gigabytes.

This feature can only be used in Advanced Edition.

When this feature is enabled, the caching strategy is to keep the cache as long as possible within the specified upper limit. If holding a new cache exceeds the limit, consider locality of reference and delete the cache from the one with the longest unreferenced time.

However, because the cache used by active transactions cannot be deleted, if a transaction uses a large number of caches, the cache may be held above the limit. In this case, delete the cache at the end of the transaction.