Let's say you've a true gift from the Oracle performance gods and reduce Oracle server time by 86%, from 7 ms down to a mind-blowing 1 ms. Even so, the users' experience will improve only from 115 ms down to 109 ms. When they don't feel the 5% end-to-end response time improvement, your achievement will not get the appreciation you think it deserves. The point is that as DBAs, our impact, while perhaps technically miraculous, may have little effect on the end-user experience.

To make matters even worse, because historically the database was the problem, end users are trained to expect it's an "Oracle problem," putting anyone remotely connected with Oracle on the defensive. It is not unusual for the DBA to reconstruct the end-to-end response time profile before the group who can make a real performance difference will get involved.

Another tricky and rarely discussed reality is that through both tracing Oracle processes or using Oracle's performance views, it is impossible to determine end-to-end response time. Let me say that again-impossible. Don't be fooled by fancy vendors or the promises of tracing and session profiling. Tracing and Oracle's performance views reach from the database server out to as far as the Oracle client process, and then stop. Beyond the Oracle client process, DBAs must use other tools to understand the remaining user experience time.