问题来自于改造的XX交易系统压测场景下数据库(AIX下Oracle 19c)出现的大量gc buffer busy release/acquire等待,如下为TPS=1100时的AWR报告。距离目标要求TPS2000还有一段差距,正是由于数据库瓶颈导致压里无法继续往上。 前10前台等待时间 - CPU占比低至 3-4% 节点1 节点2 分析思路 基于大量gc和buffer busy...
Normally CR block buffer processing does not include the ‘gc cr block flush time’. However, when a CR buffer is cloned from a current buffer that has redo pending, a log flush for a CR block transfer is required. A high percentage is indicative of hot blocks with frequent read after w...
Normally CR block buffer processing does not include the 'gc cr block flush time’. However, when a CR buffer is cloned from a current buffer that has redo pending, a log flush for a CR block transfer is required. A high percentage is indicative of hot blocks with frequent read after wr...
可以看到大量的wait class为Cluster的session,top event也看到大量的gc buffer busy acquire等待事件,该等待事件非常常见就不单独解释了,粗略计算cluster等待事件占据了dbtime的90%左右。 当遇到大量Cluster 等待事件的时候,必须先看看RAC Statistics: 1节点AWR 可以看到每秒传输的block以及message都不多,流量也并不大,所...
本案例来自某客户两节点rac的一次生产故障,现象是大面积的gc buffer busy acquire导致业务瘫痪。 首先查看1节点AWR头部信息和load profile: 1节点AWR 得到的关键信息点: 对于LCPU 256的系统,AAS=13379.42/59.91=223,说明系统非常繁忙或者遇到了异常等待。
gc buffer busy是RAC数据库中常见的等待事件,11g开始gc buffer busy分为gc buffer busy acquire和gc buffer busy release。 gc buffer busy acquire是当session#1尝试请求访问远程实例(remote instance) buffer,但是在session#1之前已经有另外一个session#2请求访问了相同的buffer,并且没有完成,那么session#1等待gc buffe...
gc buffer busy 是RAC数据库中常见的等待事件,11g开始gc buffer busy分为gc buffer busy acquire和gc buffer busy release。 gc buffer busy acquire是当session#1尝试请求访问远程实例(remote instance) buffer,但是在session#1之前已经有另外一个session#2请求访问了相
首先,回顾一下单机数据库中的'log file sync' 等待事件,当user session 提交(commit)时,user session会通知LGWR进程将redo buffer中的信息写入到redo log file,当LGWR进程完成写操作后,LGWR再post(通知)user session 写操作已经完成,user session 接收到LGWR的通知后提交操作才完成。因此user ...
小A:这次并不是,因为很多时候我们观察到系统权限类的SQL语句也在等待大规模的gc buffer busy acquire。小B:系统语句?小A:对,就是下面这个语句,他也产生了很多的GC。select event,p1,p2,p3 from v$session where sql_id='05uqdabhzncdc'EVENT P1 P2 P3--- --- --- ---gc buffer busy acquire 1 ...
gc buffer busy是RAC数据库中常见的等待事件,11g开始gc buffer busy分为gc buffer busy acquire和gc buffer busyrelease。 gc buffer busy acquire是当session#1尝试请求访问远程实例(remote instance)buffer,但是在session#1之前已经有相同实例上另外一个session#2请求访问了相同的buffer,并且没有完成,那么session#1等待...