操作系統版本：HP-UNIX B.11.31

數據庫版本：11.2.0.4 RAC

（一） 問題概要

（1）在AWR報告的Top 10 Foreground Events中發現reliable message占用了較高的DB Time，如下：

Top 10 Foreground Events by Total Wait Time
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
?????????????????????????????? Total??????? Wait???????? % DB
Event????????????????????????? Waits??????? Time Avg(ms) time?? Wait Class
------------------------------ ------------ ---- ------- ------ ----------
reliable message?????????????? 34,293,326?? 1430? 42???? 64.1?? Other
DB CPU???????????????????????? 265?????????????????????? 11.9
enq: TX - row lock contention? 2,556,859??? 114K? 45???? 5.1??? Application
PX Deq: Signal ACK RSG???????? 102,595????? 101K? 985??? 4.5??? Other
log file sync????????????????? 6,458,803??? 86.5? 13???? 3.9??? Commit
cursor: pin S wait on X??????? 184,770????? 34.8? 189??? 1.6??? Concurrent

（2）result cache被使用

SQL> show parameter result_cache_max_sizeNAME TYPE VALUE ------------------------------------ ----------- ------------------------------ result_cache_max_size big integer 5248K

（3）查詢給gv$chanel_waits顯示高等待的組件

SELECT CHANNEL, SUM(WAIT_COUNT) SUM_WAIT_COUNTFROM GV$CHANNEL_WAITSGROUP BY CHANNELORDER BY SUM(WAIT_COUNT) DESC;CHANNEL Wait Count ------------------------------------------------------ -------------- Result Cache: Channel 307718423 kxfp control signal channel 97080 RBR Channel 60807 MMON remote action broadcast channel 28256 obj broadcast Channel 14736 kill job broadcast - broadcast channel 367 parameters to cluster db instances - broadcast channel 15 Broker IQ Result 5 service operations - broadcast channel 4 quiesce Channel 2

（二）原因

如果滿足上面的3個條件，那么可以確定該等待事件由result cache處理相關的bug_19557279造成，該問題在Oracle 12.2版本中修復。

（三）解決方案

在11G中如何解決，Oracle提供了3種方案：

1.更新數據庫版本到12cR2;

2.應用補丁18416368；

3.禁用結果緩存，需要重啟數據庫實例生效

SQL> alter system set result_cache_max_size=0;

?

參考文檔：MOS上文檔ID ：1951729.1

【完】

轉載于:https://www.cnblogs.com/lijiaman/p/10520110.html

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