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Oracle Database 11gR2 Performance Tuning Cookbook

You're reading from   Oracle Database 11gR2 Performance Tuning Cookbook Shifting your Oracle Database into top gear takes a lot of know-how and fine-tuning ability. The 80+ recipes in this Cookbook will give you those skills along with the ability to troubleshoot if things starts running slowly.

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Product type Paperback
Published in Jan 2012
Publisher Packt
ISBN-13 9781849682602
Length 542 pages
Edition 1st Edition
Languages
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Author (1):
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Ciro Fiorillo Ciro Fiorillo
Author Profile Icon Ciro Fiorillo
Ciro Fiorillo
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Table of Contents (21) Chapters Close

Oracle Database 11gR2 Performance Tuning Cookbook
Credits
About the Author
Acknowledgement
About the Reviewers
www.PacktPub.com
Preface
1. Starting with Performance Tuning FREE CHAPTER 2. Optimizing Application Design 3. Optimizing Storage Structures 4. Optimizing SQL Code 5. Optimizing Sort Operations 6. Optimizing PL/SQL Code 7. Improving the Oracle Optimizer 8. Other Optimizations 9. Tuning Memory 10. Tuning I/O 11. Tuning Contention Dynamic Performance Views A Summary of Oracle Packages Used for Performance Tuning Index

Exploring optimizer hints


In this recipe, we will see how to suggest (to the optimizer) the strategy to adopt for choosing the best execution plan, using optimizer hints.

Note

The use of optimizer hints is a trick and should be considered only when no solution seems to work. The query optimizer is designed to choose the best execution plan, based on many different considerations, so it's very important to keep updated statistics to help the query optimizer in doing its work.

How to do it...

The following steps will explore optimizer hints:

  1. Connect the database to the SH schema:

    CONNECT sh@TESTDB/sh
    
  2. Set the auto-trace functionality in SQL*Plus to see only the execution plan without executing the queries:

    SET AUTOT TRACE EXP
    
  3. Select some records from the CUSTOMERS table (say, all customers born in 1949):

    SELECT
      C.CUST_FIRST_NAME, C.CUST_LAST_NAME
    FROM sh.CUSTOMERS C
    WHERE C.CUST_YEAR_OF_BIRTH = 1949;
    
  4. Execute the same query suggesting that it's better to full-scan the CUSTOMERS table in order to...

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