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.

Figure 9-2. Two other Statspack sections from the report in Figure 9-1. The timing detail and a few of the statistics in the Instance Statistics sections are shown. This is enough information to calculate the workload; that is, the arrival rate expressed in commits, transactions, logical IOs, and user calls per second.

Using the data shown in Figure 9-2, the user calls per second workload metric is calculated as follows: