R3 Performance Help!

Hi All

I am new to SAP R/3 and I have been given the lucky job of looking at R3 performance. However I have been on the ADM315 course but am still having a little difficulty finding my way around and what to look for.

I was wondering if anyone has and good white papers, websites or documents which will help me understand and get to grips with performance.

Thanking you all in advance

Phil