DB Time的说明

Time Model Statistics

• Total time in database user-calls (DB Time): 68005.2s
• Statistics including the word "background" measure background process time, and so do not contribute to the DB time statistic
• Ordered by % or DB time desc, Statistic name

Statistic Name	Time (s)	% of DB Time
sql execute elapsed time	67,999.29	99.99
DB CPU	65,614.85	96.48
PL/SQL execution elapsed time	338.06	0.50
parse time elapsed	55.33	0.08
hard parse elapsed time	45.96	0.07
hard parse (sharing criteria) elapsed time	1.01	0.00
PL/SQL compilation elapsed time	0.79	0.00
repeated bind elapsed time	0.39	0.00
connection management call elapsed time	0.14	0.00
sequence load elapsed time	0.03	0.00
failed parse elapsed time	0.02	0.00
hard parse (bind mismatch) elapsed time	0.01	0.00
DB time	68,005.25
background elapsed time	847.87
background cpu time	218.90

 

上面这个统计图来自一个awr报告。这里有个DB time。它代表什么意思了？来看看官方的解释：

 

Amount of elapsed time (in microseconds) spent performing Database user-level calls. This does not include the time spent on instance background processes such as PMON.

The most important of the time model statistics is DB time. This statistics represents the total time spent in database calls and is a indicator of the total instance workload. It is calculated by aggregating the CPU and wait times of all sessions not waiting on idle wait events (non-idle user sessions). DB time is measured cumulatively from the time that the instance was started.

Because DB time it is calculated by combining the times from all non-idle user sessions, it is possible that the DB time can exceed the actual time elapsed since the instance started up. For example, a instance that has been running for 30 minutes could have four active user sessions whose cumulative DB time is approximately 120 minutes.

For example, a instance that has been running for 30 minutes could have four active user sessions whose cumulative DB time is approximately 120 minutes.

By reducing DB time, the database server is able to support more user requests using the same resources, which increases throughput.

--大意是说DB TIME就是DB服务器花在数据库运算和等待上的时间，这里除掉了后台进程和空闲等待消耗的时间。

 

	Snap Id	Snap Time	Sessions	Cursors/Session
Begin Snap:	4327	11-6月 -09 16:42:36	23	2.0
End Snap:	4347	12-6月 -09 12:00:35	22	4.0
Elapsed:		1,157.99 (mins)
DB Time:		1,133.42 (mins)

 

     --上面这个图表大致说明了数据库的负载。