Using Skewed Performance Data To Your Advantage

• How to avoid skewed Oracle wait times and SQL elapsed times •

Using Skewed Performance Data To Your Advantage is an important seminar for all DBAs because EVERY Oracle DBA has experienced the effects of skewed performance data, but most don't know how to use that knowledge to their advantage.

Have you ever had different groups of users experience different response times from the same exact SQL? Has your IO administrator said the IO response time is fine, but you know single block IOs are taking around 25ms? If you have experienced something like this, then you have likely experienced skewed performance data.

Craig designed this seminar so you will know exactly how to avoid this situation of skewed Oracle wait times and SQL elapsed times. Craig will teach you how to gather the appropriate data, understand the data and visually demonstrate the situation.

This seminar is going to have a deep impact on your Oracle performance work. The skills Craig teaches you will help you devise a sensible solution. Join him for a practical and entertaining journey as we explore the truth about elapsed times and wait events times, turning a potential disaster into your advantage.

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What You Will Learn

  • Know what skewed data is
  • Be able to communicate why skewed data is a serious problem
  • Be able to recognize skewed data
  • Know how to gather individual wait event occurrence times, not average
  • Know six ways to gather individual SQL execution times, not average
  • Understand, demonstrate and communicate if skewed data is a problem
  • Recognize the five common statistical distributions
  • Be able to describe data using one picture and two statistics
  • Know histogram construction details
  • Know how to use the difference between the mean and median
  • Be able to install and use the free stats package, R
  • Know how a histogram can cause faulty thinking
  • Understand why v$event_histogram deceives
  • Be able to use an AWR and Statspack report to recognize skewed data problems
  • Know how to create a proper SQL execution time histogram
  • Know how to create a proper wait event occurrence histogram


  • Introduction: Revealing Deception
  • Understanding Your Data
  • Common Histograms In Oracle Performance Analysis
  • The Problem: Skewed Wait Times
  • My Advantage: Using The Skewed Wait Times
  • The Problem: Skewed Elapsed Times
  • My Advantage: Using The Skewed Elapsed Times
  • Resources And Seminar Close

Seminar Videos