For example, as shown in Figure 9-1, the time interval is an unusual 149.97 minutes. (Usually, Statspack reports are run for a single hour or two.) Therefore, the CPU capacity based on the Figure 9-6 Statspack report is as follows:

Converting to seconds, this CPU subsystem can provide 17,996.40 seconds of CPU capacity within the 149-minute interval.

Unlike when I need to gather CPU capacity, if I must determine an IO subsystem's capacity, I ask the IO administrator. As detailed in the "Gathering IO Requirements" section earlier, we have the information needed to determine Oracle's IO requirements, but determining IO capacity with authority is best done by the IO subsystem team. If your IO subsystem is simply a series of SCSI drives daisy-chained together, as was done in the 1980s and early 1990s, then simple math can be used to predict the IO subsystem's capacity. However, the combination of read and write caching and batching from both Oracle and the operating system virtually eliminates the possibility of deriving a reliable IO capacity figure. Surely, we can gather and even predict IO requirements, but predicting IO capacity is something I simply will no longer attempt.