time model 针对 oracle database 是一个非常好的特性，它能准确的反映oracle database 在某个时间内的开销。学习oracle database 必须了解其相关的概念。以下是官方文档中的定义。

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.

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

background CPU time：
Amount of CPU time (in microseconds) consumed by database background processes.

 

了解oracle database 各时间概念之间的关系

 

Response time = Service time + Wait time

 

Service time = db time + background CPU time

 

db time = cpu time + Wait time

 

Average Active Sessions= Total DB Time ÷ Elapsed Time

 

oracle 10g 可以通过V$SESS_TIME_MODEL查询相关的时间类型。

 

1) background elapsed time
      2) background cpu time
1) DB time
    2) DB CPU
    2) connection management call elapsed time
    2) sequence load elapsed time
    2) sql execute elapsed time
    2) parse time elapsed
          3) hard parse elapsed time
                4) hard parse (sharing criteria) elapsed time
                    5) hard parse (bind mismatch) elapsed time
          3) failed parse elapsed time
                4) failed parse (out of shared memory) elapsed time
    2) PL/SQL execution elapsed time
    2) inbound PL/SQL rpc elapsed time
    2) PL/SQL compilation elapsed time
    2) Java execution elapsed time