From the mid-1980s to mid-1990s, Oracle systems began to grow in size and complexity. As a result, performance analysis was needed urgently. Oracle ratio analysis was born, and the performance industry started to flourish, giving rise to technical papers, books, vendor products, and consulting services. It was kind of the cowboy days of performance analysis. Authors and consultants had a good thing going. The books on the topic were massive because of the sheer number of performance ratios. And because there were so many ratios to examine, consultants had long engagements, generating a lot of money. And since the analyses were not as exact as today, they tended to take a few more cycles to complete. In truth, not only authors and consultants benefited; anyone involved in performance analysis had plenty of work.

Now, don't get me wrong. Ratio analysis works, and at that time, it was the best method we had at our disposal. But times have changed.

The introduction of Oracle 7 in 1996 came with its kernel instrumented and allowed performance analysts a simple interface to view the instrumentation through standard SQL. I first heard about the wait interface from an Oracle internal paper by Anjo Kolk. Immediately, I began researching, testing, and validating its practical use in firefighting situations. Once convinced of its value, I began using the wait interface during my consulting engagements, writing and publishing technical papers on the subject, and speaking on the subject.1