• VISUAL EXPLAIN Analyzing SQL • EXPLAIN TOOLS Now we will see, precisely how, and how well the costly SQL executes SQL Explain Tools • Graphical ¾ Easy to quickly spot the problem ¾ Provides drill down functionality ¾ Multiple images can be stored for comparison • Text Based ¾ Can be used with any interface ¾ All the information is contained on a single screen ¾ Available on all platforms ¾ Format output with db2exfmt 22 © 2010 IBM Corporation Why use Explain? • To seek performance tuning opportunities ¾ How are tables being accessed? ¾ How useful are additional indexes? ¾ Does rewriting the query help? • Comparisons: To understand changes in query performance due to: ¾ Changes in the data model ¾ Changes in the data ¾ Changes in configuration parameters • View statistics used at time of optimization and current performance . • VISUAL EXPLAIN Analyzing SQL • EXPLAIN TOOLS Now we will see, precisely how, and how well the costly SQL executes SQL Explain Tools • Graphical