Figure 9-7 is an example of using SQL executions as the workload (logical IO would have also worked very well). The solid line is the actual sample data plotted, and the dotted line is a linear trend line added by Microsoft Excel. The correlation between the real data and the trend line is 0.9328, which represents a very strong correlation! In the upcoming sections, I will demonstrate how to use this linear relationship when anticipating the impact of a firefighting solution.

Figure 9-7. Shown is a demonstration of the linear relationship between utilization and requirements. This graph is not based on theory or mathematical formulas, but data sampled from a CPU-intensive Oracle system. The solid line is based on the actual sample data, and the dotted line is a linear trend line. Their correlation coefficient is a very strong 0.9328.

Just as with CPU utilization, IO utilization can be calculated. However, because of the possibility of file system buffer caching and IO subsystem caching, our Oracle-focused utilization calculation is a worst-case scenario (no caching assumed), includes only the instances we sample data from, and does not include any non-Oracle-related IO. So, the worth of our calculation is limited (at best). The higher worth metric is Oracle's IO requirements, which we calculated in a previous section.