Spotlight on Oracle 10.4 - Release Notes

Cache Buffer Chains Latch Wait Alarm

The Cache Buffer Chains Latch Wait alarm occurs when contention for the cache buffer chains latch exceeds a threshold.

Two main latches protect data blocks in the buffer cache.

• The cache buffer LRU chain latch must be obtained in order to introduce a new block into the buffer cache, and when writing a buffer back to disk.
• The cache buffer chains latch is acquired whenever a block in the buffer cache is accessed (pinned).

Contention for these latches usually occurs in a database that has very high I/O rates. It may be possible to reduce contention for the cache buffer LRU chain latch by increasing the size of the buffer cache. Doing this reduces the rate at which new blocks are introduced into the buffer cache.

Reducing contention for the cache buffer chains latch usually requires reducing logical I/O rates by tuning and minimizing the I/O requirements of application SQL.

You can create additional cache buffer LRU chain latches by adjusting the hidden configuration parameter _DB_BLOCK_LRU_LATCHES.

You may be able to reduce the load on the cache buffer chain latches by increasing the value of the hidden configuration parameter _DB_BLOCK_HASH_BUCKETS.

Related Topics

Tuning | Latch Page