Memory latches

The database server uses latches to control access to shared memory structures such as the buffer pool or the memory pools for the SQL statement cache. You can obtain statistics on latch use and information about specific latches. These statistics provide a measure of the system activity.

The statistics include the number of times that threads waited to obtain a latch. A large number of latch waits typically results from a high volume of processing activity in which the database server is logging most of the transactions.

Information about specific latches includes a listing of all the latches that are held by a thread and any threads that are waiting for latches. This information allows you to locate any specific resource contentions that exist.

You, as the database administrator, cannot configure or tune the number of latches. However, you can increase the number of memory structures on which the database server places latches to reduce the number of latch waits. For example, you can tune the number of SQL statement cache memory pools or the number of SQL statement cache LRU queues. For more information, see Multiple SQL statement cache pools.

Warning: Never stop a database server process that is holding a latch. If you do, the database server immediately initiates an abort.