A Quick Note
Many of these papers are for earlier versions of Oracle but many of the concepts still hold true, especially with respects to performance issues.
If you're looking to really brush up on your Oracle performance skills take a few minutes to checkout Craig Shallahamer's OraPub site.
I've chatted with Craig several times over the years and he's a great guy. He was one of the early inhouse performance guru's at Oracle. He left Oracle after many years to form his own consulting company.