I listen very closely as Oracle speaks through its wait interface. By paying close attention, I can hear Oracle clearly disclose where it hurts. With a little more information and a solid methodical approach, I can get a near-complete and clear picture of the painful situation, which allows me to develop a very specific solution set.

This chapter is the technological foundation for Oracle performance diagnosis. With this information in hand, you will be ready to dig deep into Oracle internals and diagnosis topics. I will start with a brief history of Oracle performance diagnosis. Then I'll move directly into the topics of software instrumentation, Oracle-specific instrumentation, and Oracle response-time analysis (ORTA). I will introduce both session-level, group-level, and instance-level ORTA. This is also known as profiling, but I tend to not use that word, as there is a lot of baggage associated with it.

Oracle performance diagnosis has a relatively short but interesting history. From its inception to the early 1980s, Oracle performance diagnosis was just getting started, and Oracle systems were relatively small and simplistic. As a result, SQL tuning and resolving lock contention were the focus.