Placing the collected Oracle workload data into the arrival rate formula, expressed in user calls per second, the arrival rate is 1,342.05 uc/s.

The Statspack and AWR reports calculate their load profile metrics the same way, but they store the collected data in difference tables and use different sampling techniques. For example, the Statspack facility typically collects data in 60-minute intervals and stores the data in tables starting with stats$ (the key table is stats$snap). The AWR report draws from the WRH$ tables, which contain summarized active session history (ASH) data. With just a little creativity, you can devise your own reports that pull from the Statspack or AWR tables.

Using the arrival rate formula and the Statspack data shown in Figure 9-2, we can easily perform the same load profile calculations as the Oracle Statspack developers (shown in Figure 9-1). The raw data used for the calculations is included in the Snapshot and Instance Activity Stats sections. The snapshot interval, labeled simply as "Elapsed," is expressed in minutes, which is the difference between the beginning snap time and ending snap time. The workload interval activity has been calculated and is displayed in the Instance Activity Stats section. While not shown, the interval activity is simply the difference between the ending statistic value and the beginning statistic value.