The Final Word

Abstract

The key to successful tuning with SQLT is to use SQLT regularly and for real-life problems. If you’ve reached the final chapter, you should now consider yourself a card-carrying member of the SQLT supporters club. You’ve learned a lot about what SQLT can do, and along the way you’ve probably learned some things about the cost-based optimizer and the Oracle engine. Let me remind you of some of the features we came across on our journey:

• The effect of statistics on execution plans

• The effect of skewness on execution plans

• How the optimizer transforms SQL during parsing

• How profiles can help you temporarily freeze an execution plan

• How adaptive cursor sharing works

• How dynamic sampling works

• How cardinality feedback works

• How you can use SQLT with Data Guard

• How test cases can be built with SQLT to allow exploration of the execution plans

• How to use the brute force of XPLORE to look for unexpected effects on the CBO from upgrades and other changes.

• How we can use the COMPARE method to investigate two SQLs

• Last but not least we talked about the health check script, which is a good second choice if SQLT is not available.