Figure 5-13. A simplified Oracle architecture consisting of key timing components: the end user, the user's web browser, Oracle's client process, and the Oracle server process residing on the database server. For a strong diagnosis, we need time consumed for each component and between each component.

Let's inject some time into Figure 5-13. Based on the following numbers, the true end-to-end response time is 50 ms, which is not unrealistic by today's web-based application standards.

Let's say you're an Oracle tuning hotshot. You perform a stellar OraPub 3-circle response time-based performance analysis, and reduce the Oracle server process time by 80%, from 10 ms to 2 ms. That would be an amazing feat to be sure. But think about the impact from the end user's perspective. What used to take 50 ms, now takes 42 ms. So the user experiences a 16% improvement. When the users are asked how the system is working now, they might say it feels a little faster. So, doing a fantastic database-centric tuning job did not make enough of a difference to satisfy the end user. But the situation can become even more bleak.