关于CACHE BUFFERS CHAINS描述 CACHE BUFFERS CHAINS latch is acquired when searching for data blocks cached in the buffer cache. Since the Buffer cache is implemented as a sum of chains of blocks, each of those chains is protected by a child
关于CACHE BUFFERS CHAINS描述
CACHE BUFFERS CHAINS latch is acquired when searchingfor data blocks cachedin the buffer cache.Since the Buffer cache is implemented as asum of chains of blocks, each of those chains is protectedby a child of this latch when needs to be scanned. Contentionin this latch can be caused by very heavyaccess to a single block. This can require the application to be reviewed. |
产生CACHE BUFFERS CHAINS原因
The main cause of the cache buffers chains latch contention is usually a hot block issue.This happens when multiple sessions repeatedly access one ormore blocks that are protectedby the same child cache buffers chains latch. |
CACHE BUFFERS CHAINS 处理方法
1) Examine the application to see if the execution of certain DML and SELECT statements can be reorganized to eliminate contention on the object.
处理方法如下:--通过报告确定latch: cache buffers chains 等待 Top 5 Timed Events Avg %Total~~~~~~~~~~~~~~~~~~ wait CallEvent Waits Time (s) (ms) Time Wait Class------------------------------ ------------ ----------- ------ ------ ----------latch: cache buffers chains 74,642 35,421 475 6.1 ConcurrencCPUtime 11,422 2.0logfile sync 34,890 1,748 50 0.3 Commitlatchfree 2,279 774 340 0.1 Otherdbfile parallel write 18,818 768 41 0.1 System I/O------------------------------------------------------------- --找出逻辑读高sqlSQL ordered by Gets DB/Inst: Snaps: 1-2-> Resources reportedfor PL/SQLcode includes the resources used by all SQLstatements called by the code.-> Total Buffer Gets: 265,126,882-> Captured SQL accountfor 99.8% of Total Gets CPU ElapsedBuffer Gets Executions per Exec %Total Time (s) Time (s) SQL Id-------------- ------------ ------------ ------ -------- --------- ------------- 256,763,367 19,052 13,477.0 96.8 |
