It’s been a few years since I last read this (pdf) article from Connie Dialeris Green of Oracle about how to use Statspack – and I’d forgotten how good it was.
You are bound to find a couple of details which are now outdated – it was published in 2001 and there’s a point (for example) where an updated case study would probably mention the Segment Statistics report – but as an education in how to approach Statspack, I don’t think it can be beaten.
I particularly liked the comments:
Gathering additional data usually requires skipping backwards and forwards through the report to check statistics which may be of interest.
Note that in some situations there may not be sufficient data within the Statspack report to fully diagnose the problem; in this case, it is necessary to gather additional statistics manually.
If you want to get the best out of Statspack you have to do more than take a quick look at a couple of numbers, you need to create and validate a sensible hypothesis based on all the information available. This paper instructs you in the method.