I believe Oracle response-time analysis, or ORTA for short, is the most significant performance analysis method DBAs have at their disposal.12 ORTA allows DBAs to quantify (at least in part) a user's experience, to classify time, to anticipate both the application and operating system situation, and to quantify a solution's benefit. Thus, this approach transforms the traditionally defensive firefighting posture into a forward-thinking predictive posture. That is an impressive list!

Even wait-event analysis falls short compared to ORTA, because ORTA encapsulates wait-event analysis and takes it further. Shunning the advantages of ORTA and relying solely on a wait-event analysis will limit performance analysis in depth and scope, and opens up the possibility of a misdiagnosis. Those are condemning statements, but as you read this book, you will discover that they are true. Here, I will introduce the background and concepts of ORTA. In Chapters 5 and 9, I will detail how to perform the analysis, where to gather the necessary data, and other interesting details.

Response-time analysis did not originate from the firefighting world. It is from the infrastructure planning world of IT. The infrastructure community looks at IT as a network of services and conduits to those services. Translating this to DBA-speak, that would be a bunch of servers networked together. When a user makes a request, it is routed into the mystical IT cloud, where the request waits to be serviced and receives service from a potentially large number of service providers. One way to categorize this time is to place it into two buckets: time being serviced and time waiting to be serviced, or more simply, service time and queue time. Adding the two results gives you the response time. In the course of my Oracle forecasting and predictive analysis work, I noticed that response-time analysis could be applied to firefighting.