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Jun 07, 2016 pm 03:56 PM

oneDiscover

最近发现一个奇怪的现象，数据库报告上看负载很高，但是cpu和等待事件都很低，不知道消耗的资源跑到哪里去了？ Snap Id Snap Time Sessions Cursors/Session Begin Snap: 5073 17-5月 -14 04:00:20 127 78.8 End Snap: 5074 17-5月 -14 05:13:36 363 19.5 El

最近发现一个奇怪的现象，数据库报告上看负载很高，但是cpu和等待事件都很低，不知道消耗的资源跑到哪里去了？

Snap Id	Snap Time	Sessions	Cursors/Session
Begin Snap:	5073	17-5月 -14 04:00:20	127	78.8
End Snap:	5074	17-5月 -14 05:13:36	363	19.5
Elapsed:		73.27 (mins)
DB Time:		1,196.25 (mins)

Top 5 Timed Events

Event	Waits	Time(s)	Avg Wait(ms)	% Total Call Time	Wait Class
latch: library cache	3,174	6,933	2,184	9.7	Concurrency
latch free	977	6,530	6,684	9.1	Other
latch: shared pool	4,021	1,929	480	2.7	Concurrency
cursor: pin S wait on X	82,902	1,620	20	2.3	Concurrency
CPU time		1,073		1.5

Service Statistics

ordered by DB Time

Service Name	DB Time (s)	DB CPU (s)	Physical Reads	Logical Reads
SYS$USERS	67,080.30	454.30	43,604	15,183,498
scmis	4,523.20	588.30	0	22,868,201
SYS$BACKGROUND	0.00	0.00	109	77,783

可以看到数据库软件消耗的资源不多。

找到问题症结：再看servicestatistics总的SYS$USERS消耗最多，这个是何方圣神呢？官方文档的解释：the SYS$USERS serviceis the default service name used when a user session is established withoutexplicitly identifying its service name。就是说SYS$USERS这是一个缺省的服务名，当用户的session建立的时候没有明确的标示符。

那说明此时有其他的服务在数据库服务器上跑，只有用操作系统层面上做诊断，用shell写一个top的脚本监控一下，是哪个进程导致。最后诊断出是数据库服务器在某个时间段不响应，简单的说是硬件的问题。

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