Base Statistics, Metrics, and Statistics Levels

Base statistics represent the raw data that is collected. Metrics are secondary statistical data derived from base statistics. Most of the 10g metrics are used to track the rates of change of activities in the Oracle database. Metrics are used by internal components for system health monitoring, problem detection, and self-tuning. Oracle Database 10g has metrics for session, system, file, and wait-event statistics.

The advantage of having metrics is the ready availability of data for a component to compute the rate of change related to selected activities. In previous versions, statistics had to be gathered before and after running a job to compute the changed rate for base statistics. By using metrics, the information can be derived directly after running the job.

Statistics Levels can be captured by using the statistics_level initialization parameter. This parameter has three values: BASIC, TYPICAL, and ALL.