Determine the queue time by dividing the total queue time by the unit of work value. While the detailed wait event listing is not shown, even by looking at the top four wait events shown in Figure 9-15, we can infer these account for 90% or more of all the non-idle wait time. For the necessary level of precision, I simply added the wait times for the top four wait events. Their combined wait time is 1,867 seconds during the sample interval. Here is the queue time math:

Since this system is undergoing an IO bottleneck, computing the IO utilization will not add much value and may actually cause more unimportant questions to be asked (creating unnecessary distractions).

Creating the IO response-time graph is a little tricky because you never see response time solved for the number of devices (M). Looking at the response-time equation, we know every variable except for M. We know the response time because Oracle's wait interface provides the information to calculate the queue time (Qt). It turns out this formula cannot be solved using algebra, requiring an iterative approach to converge on an answer.9