log buffer —— latch: redo writing,latch: redo allocation,latch: redo copy
来源:互联网 发布:在淘宝管控记录扣分吗 编辑:程序博客网 时间:2024/05/13 13:14
SQL> select event#,name,parameter1,parameter2,parameter3 from v$event_name where name like '%latch: redo%'; EVENT# NAME PARAMETER1 PARAMETER2 PARAMETER3---------- ------------------------------ --------------- --------------- --------------- 132 latch: redo writing address number tries 133 latch: redo copy address number tries 631 latch: redo allocation address number triesoracle为了保护将重做记录复制到重做缓冲区的一连串过程,使用以下三个锁存器。
(1)redo writing锁存器:为占用重做缓冲区内的空间,向LGWR请求写入工作的进程需要获得redo writing锁存器。因为LGWR的写入工作不能同时执行,所以自然在整个实例上只有一个。redo writing锁存器因为是独立锁存器,所以可以通过v$latch_parent视图观察活动性。
SQL> select name,gets,MISSES,IMMEDIATE_GETS,IMMEDIATE_MISSES,WAIT_TIME from v$latch_parent where name = 'redo writing';NAME GETS MISSES IMMEDIATE_GETS IMMEDIATE_MISSES WAIT_TIME------------------------------ ---------- ---------- -------------- ---------------- ----------redo writing 2072 0 0 0 0在获取redo writing锁存器的过程中,如果发生争用,就会等待latch: redo writing事件。
(2)redo copy锁存器:想要将PGA内的Change Vector复制到重做缓冲区的进程,全程都要拥有redo copy锁存器。通过v$latch_children视图可以了解redo copy锁存器的活动性。
SQL> select name,gets,MISSES,IMMEDIATE_GETS,IMMEDIATE_MISSES,WAIT_TIME from v$latch_children where name = 'redo copy';NAME GETS MISSES IMMEDIATE_GETS IMMEDIATE_MISSES WAIT_TIME------------------------------ ---------- ---------- -------------- ---------------- ----------redo copy 5 0 0 0 0redo copy 5 0 0 0 0redo copy 5 0 0 0 0redo copy 5 0 2486 6 0如果进程在获取redo copy锁存器失败,将为了获取redo copy锁存器连续尝试,在最后一次获得redo copy锁存器过程中将使用Willing-to-wait模式。若获得redo copy锁存器的过程中发生争用,则等待latch: redo copy事件。
(3)redo allocation锁存器:为了将Change Vector复制到重做缓冲区,在获取重做缓冲区空间过程中需要拥有redo allocation锁存器。通过v$latch_children视图可以了解redo allocation锁存器的活动性。
SQL> select name,gets,MISSES,IMMEDIATE_GETS,IMMEDIATE_MISSES,WAIT_TIME from v$latch_children where name = 'redo allocation';NAME GETS MISSES IMMEDIATE_GETS IMMEDIATE_MISSES WAIT_TIME------------------------------ ---------- ---------- -------------- ---------------- ----------redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0NAME GETS MISSES IMMEDIATE_GETS IMMEDIATE_MISSES WAIT_TIME------------------------------ ---------- ---------- -------------- ---------------- ----------redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 2 0 0 0 0redo allocation 4 0 0 0 0NAME GETS MISSES IMMEDIATE_GETS IMMEDIATE_MISSES WAIT_TIME------------------------------ ---------- ---------- -------------- ---------------- ----------redo allocation 8 0 0 0 0redo allocation 360 0 0 0 0redo allocation 4 0 0 0 0redo allocation 14 0 0 0 0redo allocation 52 0 0 0 0redo allocation 426 0 0 0 0redo allocation 576 3 2510 0 194已选择29行。若获取redo allocation锁存器的过程中发生争用,则等待latch: redo allocation事件。
一般情况下不常发生相关的锁存器争用。重做缓冲区的大小可能成为引起重做锁存器争用的原因。如果整个系统上创建了许多不必要的重做数据,就通过应用nologging功能减少重做数据,这也可以成为减少锁存器争用的方法。但nologging工作基本上不能恢复,请记住这一点。
- log buffer —— latch: redo writing,latch: redo allocation,latch: redo copy
- 1.latch之latch redo allocation
- latch free、buffer latch!
- Latch
- latch
- 14.4.4 Redo Log Buffer
- redo
- redo
- redo
- redo log
- Redo log
- Redo Log
- redo log
- redo log
- 理解redo(4)redo log buffer和LGWR
- buffer cache —— latch: cache buffers chains
- buffer cache —— latch: cache buffers lru chain
- 配置并使用Redo Log Buffer
- 10款iOS高效开发必备的Objective-C类库
- 一个整数数组,长度为n,将其分为m份,使各份的和相等,求m的最大值
- Servlet实现上传
- impdp使用心得
- access violation at address in module Read of address
- log buffer —— latch: redo writing,latch: redo allocation,latch: redo copy
- 采用命令行方式复制任意多个文件内容到一个文件中(华科保研机试)
- HDU1850 Being a Good Boy in Spring Festivaly
- 【解题报告】 NYOJ 78 -- 圈水池 Andrew 凸包算法
- Activity intent经常使用的 FLAG 集合(
- tar命令详解
- Oracle dbms_job package 用法小结
- POJ 1566 The Doors(计算几何+dp)
- Devexpress 绑定树