In the instance statistic views, Oracle provides only total CPU consumption. It does not differentiate between server process time and background process time.2 But if a background process is consuming an unusually large portion of the CPU, this can be easily seen from an operating system perspective. Figure 5-1 shows statistic 12, which is the total CPU consumption for the Oracle instance since instance startup. This includes all Oracle server processes and (we hope) all the background processes. The figure is in centiseconds. To convert to seconds, simply divide the queried value by 100. The example shown in Figure 5-1 has consumed 734.20 seconds (73420/100) of CPU time since it last started.

Figure 5-1. Since this instance has started, it has consumed 734 seconds of CPU. Statistic 12 from the classic instance statistics view v$sysstat contains the CPU time, in hundredths of a second, since the instance has started.

As I stressed in previous chapters, most of our diagnostic work is based on an interval of time. To capture interval activity, we need both an initial value and a final value. Figure 5-2 shows a simple example of how to capture instance CPU consumption over a 30-second interval. This strategy can be applied to any similarly structured Oracle table or view, including the performance views.