操作系统版本：HP-UNIX B.11.31
数据库版本：11.2.0.4 RAC
（一） 问题概要
（1）在AWR报告的Top 10 Foreground Events中发现reliable message占用了较高的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_size
- NAME TYPE VALUE
- ------------------------------------ ----------- ------------------------------
- result_cache_max_size big integer 5248K
（3）查询给gv$chanel_waits显示高等待的组件
- SELECT CHANNEL, SUM(WAIT_COUNT) SUM_WAIT_COUNT
- FROM GV$CHANNEL_WAITS
- GROUP BY CHANNEL
- ORDER 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
如果满足上面的3个条件，那么可以确定该等待事件由result cache处理相关的bug_19557279造成，该问题在Oracle 12.2版本中修复。
（三）解决方案
在11G中如何解决，Oracle提供了3种方案：
1.更新数据库版本到12cR2;
2.应用补丁18416368；
3.禁用结果缓存，需要重启数据库实例生效
- SQL> alter system set result_cache_max_size=0;
参考文档：MOS上文档ID ：1951729.1
【完】
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