truncate遭遇enq: RO - fast object reuse等待事件

今天truncate一个分区时明显比以前慢很多，查看进程的等待事件是enq: RO - fast object reuse，以前truncate都很快没有特意看过运行时的等待事件。

百度后找到答案：dbw0进程写回buffer cache中的脏数据块, 出现这个等待事件时运行 alter system flush buffer_cache;会有效，我没有运行当我再去看时已经执行完了

据说用dbms_stats进行分析时也可能会遇到

Applies to: Oracle Server - Enterprise Edition - Version: 10.2.0.4 This problem can occur on any platform.   Symptoms * Database has been recently upgraded from 10.2.0.1 to 10.2.0.4. * There is 'enq: RO - fast object reuse' contention when gathering schema/table statistics in parallel using DBMS_STATS package (with DEGREE>1).     Cause Bug 7385253 10.2.0.4 RDBMS 10.2.0.4 BUFFER CACHE PRODID-5 PORTID-59 Abstract: DBWR IS CONSUMING HIGH CPU   The system state dumps shows that the CKPT background process is the one holding the needed RO enqueue although it is actually doing nothing.

来自 “ ITPUB博客 ” ，链接：http://blog.itpub.net/16572356/viewspace-689702/，如需转载，请注明出处，否则将追究法律责任。

转载于:http://blog.itpub.net/16572356/viewspace-689702/