Re: Meaning of V$WAITSTAT statistics

> The Oracle 8i Reference manual Appendix A

While it describes the wait events, it doesn't tell you which ones you can safely ignore when using waits for tuning.

Even if you know which ones to focus on, the descriptions are pretty inadequate. We are informed that a "db file sequential read" means the session is waiting "while a sequential read from the database is being performed." On the other hand, a "db file scattered read" is "similar to db file sequential read, except that a session is reading multiple data blocks."

Worse, suppose one of these two waits is twice as significant in my database than the other. Does that mean I have a problem and should start using the wait interface methodologies to track down the SQL that's causing the wait event to be high? Or is it normal that in a well tuned database that the one will be higher than the other by a factor of two? Or in fact is it typical in a well tuned database that the one that appears to be the least significant should actually be much lower, so I should focus on that? Or is there really no such thing as a typical profile for a well tuned database, because various wait events might be high on your system and low on mine simply because of the way they're used, so no one really has any idea what to focus on at any given time?

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Author: Greg Moore
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