Performance Testing

I recently picked up a book titled "Troubleshooting Oracle Performance", which covers methods for tuning SQL and the Oracle DB versions 9iR2 through 11gR1. I have only read a few chapters to this point, but it appears to contain some useful information. One interesting point it makes in these early chapters is that many IT projects (BI implementations included) fail to define specific performance requirements (or SLA's) in addition to the functional requirements. In some instances, performance does not ever become an issue after implementation, but far too often, performance is not adequately tested during the test phases, and performance issues are not encountered until the application is already in production. This point is easy to ignore (until it occurs in production and it's too late), but poor performance can have the same damaging effect as functional defects on the overall user adoption of an application, and therefore performance testing should be given equal consideration as functional testing - this point is just something to think about which bares repeating every now and then.