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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 cache buffer chain (CBC) structure is used to quickly answer the question, "Is the Oracle block in the buffer cache?" Thinking about all the Oracle systems in the world today, the number of times this question is asked each day is mind-boggling. The CBC is essentially a searching structure. There are many search algorithms for Oracle to choose from, but for reasons I'll detail in Chapter 6, Oracle chose what is known as a hashing structure. Figure 3-5 is an example of a hashing structure. Figure 3-5. A hashing structure can be used to quickly locate (search for) a specific object. The memory chains shown in option A on the left are protected by a single latch, whereas with option B, the chains are protected by three latches. 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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