Requirements can also be articulated in terms of more traditional Oracle workload metrics like user calls, SQL statement executions, transactions, redo bytes, and logical IO. For example, referring to the workload profile shown in Figure 9-1, which is based on v$sysstat, the workload can be expressed as 415 uc/s, 0.22 trx/s, 145,325 LIO/s, or 22,926 redo bytes generated per second. Referring to Figure 9-2, the system requirements can also be expressed as 1,675,794 centiseconds (16,757.94 seconds) of CPU consumed over the 149.97-minute interval. This means on average every second, the Oracle instance consumed 1.862 seconds of CPU, which is a simpler way of saying 1.862 CPU seconds consumed per second. At first, it may seem strange to speak of CPU consumed like this, but it is very correct and sets us up for the next topic, which is capacity.

Once the definition of requirements is set, the data must be collected. Most Oracle systems now collect Statspack or AWR data, which means the data collection is currently occurring for you. Your job is to extract the necessary information.

When gathering CPU requirements, we typically look at the time model system statistics (v$sys_time_model) or the instance statistics (v$sysstat). In previous chapters, I have presented how to gather CPU requirements from the v$sesstat, v$sysstat, v$ses_time_mode, and v$sys_time_model views.