Time and Wait Model
We briefly mentioned the Time and Wait model earlier, while introducing the performance-reporting philosophy new to Oracle Database 10g. In essence, in this version, metrics and statistics are classified by type of usage of CPU for the Time component and by type of waiting for the Wait component. In other words, the previous equation for response time can now be restated in its two component forms as follows:
Response Time = ∑ CPU Consumption by Class + ∑ Wait Time by Class
The difference is that now you can determine CPU time spent in various subcomponents (class of consumption) as well as time spent waiting for various classes of events. A quick look at the V$SYS_TIME_MODEL and V$SYSTEM_WAIT_CLASS views helps explain this ...
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