We have already touched on gathering capacity data in a number of areas of this book, so I will make this brief. The trick to quantifying capacity is defining both the unit of power and the time interval. For example, the time interval may be a single hour, and the unit of power may be 12 CPU cores. Combining the time interval and the power unit-12 CPU cores over a 1-hour period of time-we can say the database server can supply 720 minutes of CPU power over a 1-hour period (12 CPUs _ 60 minutes) or 43,200 seconds of CPU power over a 1-hour period (12 CPUs _ 60 minutes _ 60 seconds / 1 minute).

A very good way to quantify CPU capacity is based on the number of CPU cores.1 The number of CPU cores can be gathered from an operating system administrator. Additionally, the v$osstat view is available with Oracle Database 10g and later versions. While obvious in the particular Statspack report shown in Figure 9-6, Oracle does not always clearly label the number of CPU cores. In this case, you can usually spot the value that represents the number of CPU cores, but you should always double-check, because the number the CPU cores is so important. It is used to calculate the database server's CPU capacity and is a key parameter when calculating capacity and utilization. Figure 9-6 indicates there are two CPUs, but in reality, there is a single dual-core CPU providing two CPU cores' worth of processing power.

Figure 9-6. Shown is the operating system statistics portion of the same Statspack report shown in Figures 9-1, 9-2, 9-3, and 9-5. This particular database server has a single dual-core CPU.