Posts About Webinars
Morton has the following posts about her first webinar:
- July 31 Webinar—original advert for first webinar
- Diagnosing SQL Performance Problems Webinar Followup for slides and scripts.
Diagnosing SQL Performance Problems
Webinar is available via a form at Diagnosing SQL Performance Problems with Karen Morton.
Is The Problem Inside Or Outside The Database?
Remember to check the operating system statistics in the AWR report.
Points to remember:
- Check for no statistics
- Poor statistics collection—defaults are better in 11.2
- “Collect too frequently”
- “Collect too many histograms (or not enough)”
- “Dynamic sampling disabled”
“Revert to previous statistics”
Identified in AWR SQL reports, or specialised query to find unstable queries.
Check for plan changes first. Find out why the plan changed. Need a longer AWR retention.
3 Most Common Rewrite Reasons
- Query transformation problems
- Datatype “oddities” or complex expressions
- Procedural vs set-based approach