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Oracle SQL Tuning with Oracle SQLTXPLAIN by Stelios Charalambides

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CHAPTER 4

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How Skewness Can Make Your Execution Times Variable

Skewness is one of those topics that for some reason is often ignored, or misunderstood. Skewness is an important part of data handling for the cost-based optimizer. It makes a difference as to what the optimizer decides to do. It is so important that Oracle created new features such as Adaptive Cursor Sharing just to handle the consequences of skewness.

Skewness

In this section we are going to look at what skewness is, how it comes about, and how it affects your execution plan. If you handle skewness every day, you’re likely to know immediately what kind of situations are likely to ...

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