oracle awr快照点不记录问题

alert日志里发现
Suspending MMON slave action kermrfsa_ for 82800 seconds

mmon的trc
KEWRAFC: Flush slave failed, AWR Enqueue Timeout

手动建快照点
exec dbms_workload_repository.create_snapshot;

等待为
reliable message

reliable message的方法
在 v$even{t}_{n}ame视图中，我们可以找到该事件的三个参数的含义，三个参数分别代表channelcontext，channelhandle，broadcastmessage，获得这三个参数，就能够做出一定的判断：SQL>selectname,parameter1,parameter2,parameter3fromv$event_name where name=‘reliable message’;

NAME PARAMETER1 PARAMETER2 PARAMETER3

---

reliable message channel context channel handle broadcast message

例如：在出现等待时，通过以下查询，获得 reliable message 的 P1 参数：

select to_char(p1, ‘XXXXXXXXXXXXXXXX’) event_param,
count(), sum(time_waited/1000000) time_waited
from gv$active_session_history
where event = ‘reliable message’
group by to_char(p1, ‘XXXXXXXXXXXXXXXX’)
order by time_waited desc
EVENT_PARAM COUNT() TIME_WAITED

---

   3CCF8A1D8                                          572  904.548231
   3CCF96200                                          109   69.145101
   3CCF9AFF0                                           54   23.987554

通过 x$ksrcdes 可以找到 P1 参数代表的通道信息：

select name_ksrcdes
from x$ksrcdeswhereindx=(selectnam{e}_{k}srcctxfromx$ksrcctx where addr like ‘%&addr%’);
SQL> /
Enter value for addr: 3CCF8A1D8
NAME_KSRCDES

RBR channel

进一步的通过 GV$CHANNEL_WAITS 可以查看数据库的各种类等待。

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

CHANNEL SUM_WAIT_COUNT

---

Result Cache: Channel 429264591

这个问题是结果集缓存的Bug导致的，Bug号为19557279，该问题在Oracle 12.2版本中修复。参考：
Very High Waits for ‘reliable message’ After Upgrade to 11.2.0.4 When Using Result Cache (Doc ID 1951729.1)
如果未使用结果集缓存特性，可以通过临时关闭来解决：
SQL> alter system set result_cache_max_size=0;

System altered.

最终发现
MMON remote action broadcast channel

kill掉mmon进程

启停限制会话（会造成业务连不进来一下）
ALTER SYSTEM enable restricted session;
ALTER SYSTEM disable restricted session;