要查看的关键数据库统计信息是日志文件并行写入和日志文件同步等待事件的系统级TIME_WAITED和AVERAGE_WAIT,因为它们是相互关联的: SQL> select event,time_waited,average_wait from v $ system_event where('log file parallel write','log file sync'); EVENT TIME_WAITED AVERAGE_WAIT --- --- --- log fi...
要查看的关键数据库统计信息是日志文件并行写入和日志文件同步等待事件的系统级TIME_WAITED和AVERAGE_WAIT,因为它们是相互关联的: SQL> select event,time_waited,average_wait from v $ system_event where('log file parallel write','log file sync'); EVENT TIME_WAITED AVERAGE_WAIT --- --- --- log fi...
As the db file parallel write wait event belongs only to the DBWR process, the log file parallel write wait event belongs only to the LGWR process. Although user sessions never experience the log file parallel write wait event, they can be impacted by a slow LGWR process. A slow LGWR proc...
上面time_waited、average_wait的单位为百分之一秒(in hundredths of a second), 'log file parallel write'事件的平均等待时间大于 10ms (or 1cs),这通常意味着存在较慢的I/O吞吐量。 LGWR进程写入慢会影响用户事务提交的时间。 If the log file parallel write average wait time is greater than 10ms (o...
(4)调整db_file_multiblock_read_count值,以达到每次读取更多数据块的目的。 第五个为log file parallel write,log file sync,db file async I/O submit基本为一类,log file parallel write,log file sync只能通过改善IO性能来提升了,关于db file async I/O submit,该等待跟oracle的异步io有关。
二.log file parallel write等待事件 引自如下blog: http://oracle-dox.net/McGraw.Hill-Oracle.Wait.Interf/8174final/LiB0036.html log file parallel write The log file parallel write wait event has three parameters: files, blocks, and requests.In Oracle Database 10g, this wait event falls under ...
lock manager wait for remote message waittime not used not used log buffer space not used not used not used log file parallel write files blocks requests log file sequential read log# block# blocks log file single write log# block# blocks log file switch (archi...
Wait Event Histogram Detail (4 sec to 2 min)、Wait Event Histogram Detail (4 min to 1 hr),值得注意的是,几个直方图的关系并不是加总的关系,前面的是总等待次数,后面的指标是百分比情况。 等待事件直方图主要看总等待次数比较多的和消耗时长比例最高的那些事件即可,本文继续按照数据统计原则进行四个直方图...
Top 5events里面,log file sync贡献了12.1%的DB time, 当然还有其它的一些latch等待,这些是另外需要分析优化并解决的话题,本篇先不做讨论。 Cpu 使用率100%: 各位看官请继续先忽略其它event,这里看过来: logfile sync平均等待时间44ms logfile parallel write平均等待时间9ms。
时间并不高,假设是存储IO问题,那么这个event的平均等待时间应该是比較高才对。 我们能够看到log file sync和log file parallel write的waits都是差点儿相同的。可是log file parallel write的avg wait time只唯独4ms,这是一个正常的值。也就是说能够我们排除存储IO问题。