Take a close look at Figure 1-1, which illustrates the 3-circle analysis technique. In a nutshell, the database server is divided into three subsystems: Oracle, application, and operating system. Each subsystem is diagnosed separately and then in combination. There will be a clear overlap in resource consumption and contention. If the problem resides with the database server, the overlap is the current performance problem. It's that simple.

Figure 1-1. As unbelievable as it may seem, OraPub's 3-circle analysis method will guide you toward pinpoint diagnosis, reduce your chances of making a mistake, help you determine multiple solutions, help you structure your analysis, and help you effectively communicate your findings.

The Oracle subsystem is focused on the Oracle instance and database. Oracle response-time analysis (discussed later in this chapter) is used to diagnose this circle, and solutions are directly targeted at what can be done to improve the Oracle response time. The application subsystem is focused on SQL, application processes, programs, modules, and so on. The Oracle response-time analysis will direct you to what type of SQL is causing contention in Oracle, and probably consuming a tremendous amount of operating system resources.