One of the most important challenges faced by Oracle database administrators and Oracle developers is the need to tune SQL statements so that they execute efficiently. Poorly tuned SQL statements are one of the leading causes of substandard database performance and poor response time. SQL statements that perform poorly result in frustration for users, and can even prevent a company from serving its customers in a timely manner.

In this book, Mark Gurry shares his in-depth knowledge of Oracle's SQL statement optimizers. Mark's knowledge is the result of many hard-fought tuning battles during his many years of providing Oracle tuning services to clients. Mark provides insights into the workings of the rule-based optimizer that go well beyond what the rules tell you. Mark also provides solutions to many common problems that occur with both the rule-based and cost-based optimizers.

In addition to the specific problem/solution scenarios for the optimizers, Mark provides a number of handy SQL tuning tips. He discusses the various optimizer hints, telling you when they can be used to good effect. Finally, Mark discusses the use of the DBMS_STATS package to manage database statistics, and the use of outlines to specify execution plans for SQL statements in third-party applications that you can't otherwise modify.

Contents

Introduction

The SQL Optimizers

Understanding the Rule-Based Optimizer

Understanding the Cost-Based Optimizer

Some Common Optimizer Misconceptions

Which Optimizer to Use?

Rule-Based Optimizer Problems and Solutions

Problem 1: Incorrect Driving Table

Problem 2: Incorrect Index

Problem 3: Incorrect Driving Index

Problem 4: Using the ORDER BY Index and notthe WHERE Index

Cost-Based Optimizer Problems and Solutions

Problem 1: The Skewness Problem

Problem 2: Analyzing with Wrong Data

Problem 3: Mixing the Optimizers in Joins

Problem 4: Choosing an Inferior Index

Problem 5: Joining Too Many Tables

Problem 6: Incorrect INIT.ORA Parameter Settings

Problems Common to Rule and Cost with Solutions

Problem 1: Statement Not Written for Indexes

Problem 2: Indexes Are Missing or Inappropriate

Problem 3: Use of Single-Column Index Merge

Problem 4: Misuse of Nested Loop, Sort Merge,or Hash Join

Problem 5: Misuse of IN, EXISTS, NOT IN, NOT EXISTS,or Table Joins

Problem 6: Unnecessary Sorts

Problem 7: Too Many Indexes on a Table

Problem 8: Use of OR Instead of UNION

Problem 9: Tables and Indexes with Many Deletes

Other Problems: Heavy Usage of Views

Other Problems: Joining Too Many Tables

Handy SQL Tuning Tips

Identify Bad SQL

Identify Long-Running SQL Statements

Use DECODE for IF/ELSE Selection

Encourage Bind Variables

Using SQL Hints

When Are Hints Ignored?

Using Hints in Views

Available Hints

Using DBMS_STATS to Manage Statistics

Using DBMS_STATS to Analyze Faster

Copying Statistics Using DBMS_STATS

Manipulating Statistics Using DBMS_STATS

Reverting to Previous Statistics

Using Outlines for Consistent Execution Plans

Recording Outlines

Enabling Outlines

Managing Outlines

Type produit : Ouvrage Langue : Anglais   Editeur(s) : O'Reilly Auteur(s) : Mark Gurry   ISBN13 : 978-0-596-00268-8 EAN13 : 9780596002688 ISBN10 : 0-596-00268-8

Parution : 11/03/2002 Edition : 1ère édition   Nb de pages : 102 pages Format : 11 x 17,5 Couverture : Broché Poids : 109 g Intérieur : Noir et Blanc