Trouble-Shooting
It is easy to waste time when trouble-shooting because you don't have a clear idea of what you are trying to achieve, and which tools are most appropriate.
This presentation outlines the three main targets of trouble-shooting, and describes the different strategies needed to address them.
The presentation will not go to great lengths to describe the statistics that the database can report; that topic will be part of another presentation.
After seeing this presentation, you should have a better idea of where and how to invest your time when faced by performance problems.