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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. ------------------------------- Fortunately, by default, Oracle creates thousands of CBC latches. While Figure 6-9 shows 3 latches, real Oracle systems will have at least 10,000 chains and 1,000 latches. One way to look at the contention possibility is to calculate how many chains each latch protects. For example, if there are 10,000 chains and 1,000 latches, then each latch ensures serialization for 10 chains. Table 6-1 shows a few samples of the relationship between data buffers, CBCs, and the CBC latches. Each sample was taken from a real production Oracle system. Only the number of data buffers was set; that is, all the other values were defaults based on the number of data buffers. Based on the number of data buffers, Oracle determines the number of hash chains and the number of 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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