oracle waits performance events waitevents

May 4th: some updates after discussion with Jeff Holt, Cary Millsap and Ron Christo of Method-R.

There’s all the documentation, and there all the terrific blogs about performance and Oracle wait events. But if you more or less start with this stuff, or encounter a wait event that is not (extensive enough) documented, or an event turns up and gives a response time you don’t expect, you need to understand what that wait event means. If you don’t know, it’s easy to get stuck at this point.

If you are familiar with waits, and just want to dig further, progress to “Get to know wait events”, if you want to get up speed with waits, read on.

What is a wait event?

This is the definition of the performance tuning guide in the Oracle documentation: