MySQL Opens and Closes Tables
MySQL Opens and Closes Tables ,
table_cache is related to max_connections. For example, for 200 concurrent running connections, you should have a table cache size of at least 200 * N, where N is the maximum number of tables per join in any of the queries which you execute. You must also reserve some extra file descriptors for temporary tables and files.
->When the cache is full and a thread tries to open a table that is not in the cache.
->When the cache contains more than table_cache entries and a table in the cache is no longer being used by any threads.
->When a table flushing operation occurs. This happens when someone issues a FLUSH TABLES statement or executes a mysqladmin flush-tables or mysqladmin refresh command.