Figure 4-5. Numerically, on a two-CPU core system, queuing accounts for 10% of response time at around 32% busy. Just as with Figure 4-3, when the system busyness exceeds 100%, queue time becomes infinite.

Figure 4-6. Graphically, on a two-CPU core system, queuing doesn't look like an issue until around 65% busy. It's more difficult to make a risk assessment because the response-time curve does not have such a dramatic elbow as systems with more CPU cores.

DBAs who have control over the workload entering their system have been known to run the CPUs as busy right up to the beginning of the elbow of the curve. Now, not many administrators have this kind of workload control. But if your system runs a combination of online transaction processing (OLTP) and batch processes, then it's likely you can play this game yourself. Let's look at how.