首页 > Linux操作系统 > Linux操作系统 > 关于AWR 中DB time
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.
/*记住:如果只有一个cpu,就不可能4个session同时处于no-idle,所以下面这个假设只能在大于4cpu的服务器上成立。
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.
Report A:
Snap Id Snap Time Sessions Curs/Sess
--------- ------------------- -------- ---------
Begin Snap: 4610 24-Jul-08 22:00:54 68 19.1
End Snap: 4612 24-Jul-08 23:00:25 17 1.7
Elapsed: 59.51 (mins)
DB Time: 466.37 (mins)
Report B:
Snap Id Snap Time Sessions Curs/Sess
--------- ------------------- -------- ---------
Begin Snap: 3098 13-Nov-07 21:00:37 39 13.6
End Snap: 3102 13-Nov-07 22:00:15 40 16.4
Elapsed: 59.63 (mins)
DB Time: 19.49 (mins)
/sbin> bindprocessor -q先说Report A,在snapshot间隔中,总共约60分钟,cpu就共有60*8=480分钟,DB time为466.37分钟,则:
The available processors are: 0 1 2 3 4 5 6 7
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