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by Craig Shallahamer Get the book here |
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Craig Shallahamer's Blog
The text below is an except from the book, Oracle Performance Firefighting, written by Craig Shallahamer of OraPub, Inc. Figures and tables are not included on this page, only their reference. To order the book in either print or PDF form, click here. ©2009, 2010 by Craig Shallahamer. This is copyrighted material. Please—Out of respect for those involved in the creation of the book and also for their familes, we ask you to respect the copyright both in intent and deed. Thank you. ------------------------------- Queue time can be calculated a number of ways. The simplest way, which is sufficient for our purposes, is to subtract the service time from the total request time: The total request time is more formally called response time and is discussed in the next section. The units for queue time are the same as for service time, such as milliseconds per logical IO. Looking at the classic utilization formula, you see that utilization can increase if the service time, the queue time, or both increase. As the classic utilization formula indicates, and as Figure 9-7 demonstrates occurs in CPU-intensive Oracle systems with a consistent workload mix, when utilization increases, it is because the arrival rate (the workload) is increasing, not because service time is increasing. Please—Out of respect for those involved in the creation of the book and also for their familes, we ask you to respect the copyright both in intent and deed. Thank you. |
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