Referencing Figure 4-7, the CPU subsystem is busy around 25% of the time; that is, it's idle around 75% of the time. There appears to be plenty of available CPU capacity; that is, the operating system's CPU capacity has exceeded Oracle's requirements.

Figure 4-8 shows another common way to get CPU utilization. The sar (System Activity Report) command is a wide-reaching performance monitoring facility available on every Linux/Unix system. However, some operating system administrators do not install the required sar package or allow DBAs to run an interactive sar report. 2 When sar is installed, it continually monitors system activity and stores the results for later retrieval. Operating system administrators tend to reference historical sar data, whereas most DBAs want to run sar interactively to view the system as it is currently operating. So when you tell your administrator you want to "run sar," make sure he knows you want to run it interactively and only when necessary. The sar output can also be directed to a file for later processing (think awk and grep).

Figure 4-8. A sample sar output sampling every 15 seconds on an active Oracle system. There is plenty of idle time, so the system has plenty of CPU capacity.