FROMv$rowcache r ORDER BY1, 4,5; 查看row cache objects具体包含的内容。 SET PAGES 1000 COLUMN cache# FORMAT 99999 COLUMN nameFORMAT a33 COLUMN latch# FORMAT 999999 SELECTDISTINCTs.kqrstcln latch#, r.cache#, r.parameter name, r.TYPE, r.subordinate# FROMvrowcacher,xkqrst s WHEREr.cache#...
Row cache objects latch: 当用户进程访问缓存的数据字典数值时,将使用Row cache objects latch。 下 面我们将着重介绍一下如何检测和减少redo log buffer latch的冲突。对redo log buffer的访问是由redo log buffer latch来控制的,这种latch有两种类型, redo allocation latch和redo copy latch。 Redo allocation lat...
This latch comes into play when user processes are attempting to access or update the cached data dictionary values. Solutions Problem: To determine if the row cache is being used efficiently, execute the following SQL. If the ratio is not close to 1 then some tuning required. SELECT parameter...
cache buffers lru chain闩锁竞争与解决当用户进程需要读数据到buffer cache时,或cache buffer根据lru算法进行管理时,就不可避免地要扫描lru list获取可用buffer或更改buffer的状态,我们知道,oracle的buffer cache是共享内存,可以为众多并发进程并发访问,所以在搜索的过程中必须获取latch(latch是oracle的一种串行锁机制,用于...
在Active dataguard遇到latch: row cache objects 查询如下语句 select a.SAMPLE_TIME,a.SQL_ID,a.EVENT,a.P1TEXT,a.P1,a.P2TEXT,a.P2,a.P3TEXT,a.P3, b.f2 from vacti,(ectmax(b.SQLTEXT)f2,sqdfrmvsql b group by sql_id ) b where a.sql_id = b.sql_id ...
也可能是虽然有空闲空间,但是由于应用重启、或者准点抢售类的应用导致高并发事务进入数据库后,短暂时间内需要将大量的undo seg从offline变成online,而smon没有处理得那么快,故可能出现短暂的大量enq:US-contention,这个时候通常会伴随大量的'latch: rowcache objects'(on DC_ROLLBACK_SEGMENTS)。我们的一个保险类系统...
也可能是虽然有空闲空间,但是由于应用重启、或者准点抢售类的应用导致高并发事务进入数据库后,短暂时间内需要将大量的undo seg从offline变成online,而smon没有处理得那么快,故可能出现短暂的大量enq:US-contention,这个时候通常会伴随大量的'latch: rowcache objects'(on DC_ROLLBACK_SEGMENTS)。我们的一个保险类系统...
这次处理的案例,最为典型的等待表征就是:latch row cache objects 和 cursor:pin s wait on X: Top 5 Timed Events EventWaitsTime(s)Avg Wait(ms)% Total Call TimeWait Class latch: row cache objects 475,336 127,021 267 48.2 Concurrency db file sequential read 8,350,230 45,113 5 17.1 User ...
from client0110622253SQL*Net message to client0110623116db file sequential read9110624257SQL*Net message from client0110625253SQL*Net message to client011062667read by other session6110627116db file sequential read11110628116db file sequential read1110629205latch:row cache objects91106210212latch:library cache51...