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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. ------------------------------- Suppose the IO administrator told you the IO subsystem has a capacity of 250 IOPS. Earlier, in the "Gathering IO Requirements" section, we calculated that, during the reporting interval, Oracle processes generate 5.59 IOPS. Once again, using the utilization formula, we have this calculation: So, while the CPU subsystem is running at 100% utilization, if the IO subsystem is receiving only this specific Oracle instance's IO requests, and assuming there is no non-Oracle caching, the IO subsystem would be running at around 2.2% utilization. It appears the IO subsystem has plenty of capacity. Service time is how long it takes a single arrival to be served, excluding queue time. If the arrival is defined to be an Oracle user call, then the service time may be something like 4.82 milliseconds per user call, or 4.82 ms/uc. 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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