Re: Why wait?

> Thats fine for expensive sql...but waits can be a
> whole lot more than that...

Agreed. I'm just asking about "db file scattered read" and "db file sequential read." What's the purpose of using the wait interface to investigate these two events?

The accounts I've read of drilling down through the wait interface views make it seem like you're hot on the trail of Dr. Evil. But in fact these two wait events *don't* lead you to poorly tuned SQL, just SQL that does a lot of physical reads and happen to be popular at the time you looked at v$session_wait.

What's more, using the wait views to find such SQL seems to be a very catch-as-catch-can kind of affair. Maybe an SQL statement that does a lot of physical reads is running when you look, maybe it isn't.

If your goal is to find SQL that does a lot of physical reads, why not forget about these two events? Just go to v$sql and sort by physical reads. Now you have a comprehensive picture of what's going on.

If your goal is something else, then what is it? Is it ever worthwhile to use the wait views to investigate these two wait events - "db file scattered reads" and "db file sequential reads"?

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Author: Greg Moore
  INET: sqlgreg_at_pacbell.net

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