如何优化latch: cache buffer chains

[blackcat242]

在awr报告中，latch: cache buffer chains占用的时间基本是前三的，这个要如何优化？在网上看说是有参数可以修改latch数量，但是这个参数在11.2中已经是隐藏参数了。还有其它办法么

[yuppy]

优化方向弄错了吧，应该去查查 逻辑读比较高的、低效率的SQL才是根本吧。

[小灰狼W]

"latch: cache buffers chains" contention is typically encountered because SQL statements read more buffers than they need to and multiple sessions are waiting to read the same block. If you have high contention, you need to look at the statements that perform the most buffer gets and then look at their access paths to determine whether these are performing as efficiently as you would like. Typical solutions are:- .Look for SQL that accesses the blocks in question and determine if the repeated reads are necessary. This may be within a single session or across multiple sessions. .Check for suboptimal SQL (this is the most common cause of the events) - look at the execution plan for the SQL being run and try to reduce the gets per executions which will minimize the number of blocks being accessed and therefore reduce the chances of multiple sessions contending for the same block.

[lbf_19881016]

首先查询是在哪个对象上出现闩锁latch，具体到那些sql语句，然后进行优化。