Why Has My Plan Changed. Top 7 Plan Stability Pitfalls and How To Avoid Them!

Neil Chandler
engNeil Chandler
Chandler Systemsace director

 

Abstract

When you write SQL, Oracle runs it through the Optimiser to determine the fastest way to access the data. This access path sometimes changes without anyone noticing. Sometimes it's faster. Sometimes it's slower. Dramatically, catastrophically slower. Why doesn't Oracle always get it right? Why does it change?

This presentation will answer the question Why - through the use of live demonstrations, and explain what we can do to manage SQL execution plans within the database and minimise the opportunity for Oracle to get it wrong.