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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. ------------------------------- The AWR Instance Statistics section showed the physical read IO requests (breads for short) statistic to be 148,439. Before we calculate the service and queue times, the arrival rate based on our unit of work needs to be calculated. Here is the arrival rate math: Based on Figure 9-14, the total service time is 2,091.82 seconds, or 2,091,820 milliseconds. Determine the service time by dividing the total service time by the unit of work value. Here is the service time math: 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: 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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