Heavy load and database statistics

Hi,
I found that the sum of statistics "CPU used by this session" (V$SESSTAT) and sum of all waits from V$SESSION_EVENT (for a given session) are equal to the "clock on the wall" time from this session (if the session is at least a few minutes long). This makes sense: server process is either consuming CPU cycles or waiting on something like IO or message from client program.

Clock on the wall time = CPU time + sum(Time_Waited).

Lets assume that I am running something like SELECT count(*) FROM ... WHERE script
in SQL*Plus so there will be no enqueue waits (no locks), no "SQL*Net Message from client" waits, etc,
and the only type of waits will be IO waits ("db file sequential/scattered read').

Now, if I run the same job under heavy load (CPU-bounded system) Clock on the wall time
will definitely increase, and CPU time will be the same. So, the IO waits will increase. Isn't it misleading?

In other words, how to separate the "true IO" waits from "true CPU waits"? Does this question make sense?

Thanks,
Sev Received on Mon Sep 13 1999 - 02:57:44 CDT