一.背景

最近有个客户的系统从windows迁移到了linux 11.2.0.4，取awr报告发现在top 10里面有个不常见的等待事件Reliable Message。

二.排查

排查的时候参考了盖老师的这篇文章。最终根据现象在mos上找到了答案。
https://www.modb.pro/db/6288

3.1.排查记录如下

SQL> select name,parameter1,parameter2,parameter3 from v$event_name where name='reliable message';

NAME
----------------------------------------------------------------
PARAMETER1
----------------------------------------------------------------
PARAMETER2
----------------------------------------------------------------
PARAMETER3
----------------------------------------------------------------
reliable message
channel context
channel handle
broadcast message

SQL> select to_char(p1,'XXXXXXXXXXXXXXXX') event_param,count(*),sum(time_waited/1000000) time_waited
  2  from gv$active_session_history 
  3  where event = 'reliable message'
  4  group by to_char(p1,'XXXXXXXXXXXXXXXX')
  5  order by time_waited desc;

EVENT_PARAM	    COUNT(*) TIME_WAITED
----------------- ---------- -----------
	547234D90	  66	44.16994
	54722FD68      10414   11.909444
	54722FC00	  29	 .011586
	547223180	   2	 .000589

SQL> 

SQL> select name_ksrcdes from x$ksrcdes where indx=(select name_ksrcctx from x$ksrcctx where addr like '%&addr%');
Enter value for addr: 54722FD68
old   1: select name_ksrcdes from x$ksrcdes where indx=(select name_ksrcctx from x$ksrcctx where addr like '%&addr%')
new   1: select name_ksrcdes from x$ksrcdes where indx=(select name_ksrcctx from x$ksrcctx where addr like '%54722FD68%')

NAME_KSRCDES
----------------------------------------------------------------
Result Cache: Channel

3.2.进一步排查（我没查，就查到了上一步）

SELECT CHANNEL,
SUM(wait_count) sum_wait_count
FROM GV$CHANNEL_WAITS
GROUP BY CHANNEL
ORDER BY SUM(wait_count) DESC;

三.相关mos文档

3.1.Doc ID 1951729.1

Very High Waits for ‘reliable message’ After Upgrade to 11.2.0.4 When Using Result Cache (Doc ID 1951729.1)

3.2.SOLUTION

1.Upgrade to a higher version where the issue is fixed i.e. Oracle 12c release 12.2 or the 12.1.0.2.0 Patchset

2.Apply patch 18416368 if available on your platform

3.To workaround the issue, disable result cache by setting the following parameter:
SQL> alter system set result_cache_max_size=0;
The instance(s) must be restarted for the parameter to take effect.

3.3.文档链接

Doc ID 1951729.1
https://www.modb.pro/doc/59147