cache buffers LRU chain latch等待事件

This latch is needed when user processes try to scan the LRU (least recently used) chain containing blocks in the buffer cache. This latch must be acquired before the block can be inserted into (when the block is read in from the disk) or taken out of the LRU chain (when the block is written down to the disk).  

Solutions

• Consider implementing multiple buffer pools to reduce contention on this latch.
• Increase the number of LRU latches with the parameter DB_BLOCK_LRU_LATCHES. Generally the default value works.
• Reduce data blocks visited by a query and thereby reduce LRU latch requests in the buffer pool by tuning the SQL.