Book Image

Oracle Database 11gR2 Performance Tuning Cookbook

By : Ciro Fiorillo
Book Image

Oracle Database 11gR2 Performance Tuning Cookbook

By: Ciro Fiorillo

Overview of this book

Oracle's Database offers great performance, scalability, and many features for DBAs and developers. Due to a wide choice of technologies, successful applications are good candidates to run into performance issues and when a problem arises it's very difficult to identify the cause and the right solution to the problem. The Oracle Database 11g R2 Performance Tuning Cookbook helps DBAs and developers to understand every aspect of Oracle Database that can affect performance. You will be guided through implementing the correct solution in a proactive way before problems arise, and how to diagnose issues on your Oracle database-based solutions. This fast-paced book offers solutions starting from application design and development, through the implementation of well-performing applications, to the details of deployment and delivering best-performance databases. With this book you will quickly learn to apply the right methodology to tune the performance of an Oracle Database, and to optimize application design and SQL and PL/SQL code. By following the real-world examples you will see how to store your data in correct structures and access and manipulate them at a lightning speed. You will learn to speed up sort operations, hack the optimizer and the data loading process, and diagnose and tune memory, I/O, and contention issues. The purpose of this cookbook is to provide concise recipes, which will help you to build and maintain a very high-speed Oracle Database environment.
Table of Contents (21 chapters)
Oracle Database 11gR2 Performance Tuning Cookbook
Credits
About the Author
Acknowledgement
About the Reviewers
www.PacktPub.com
Preface
Index

Introduction


In this chapter, we discuss the query optimizer, which is a built-in component of the Oracle database. The optimizer chooses the most efficient way to execute a SQL statement, using three steps:

  1. Query transformation.

  2. Estimation.

  3. Plan generation.

The query transformation step accepts the parsed statement, divides it into query blocks (for example, identifying a subquery), and determines if it's better to transform the query blocks into a different SQL statement—semantically equivalent—that can be processed in a more efficient way.

The estimator determines the overall cost of an execution plan, based on selectivity, cardinality, and the cost of each operation involved in the plan. If statistics are available, the estimator uses them for computation, improving the accuracy of the result.

The plan generator explores various plans for each query block, due to various factors: different access paths, joins, and/or join order. We can follow many paths to answer a query; the plan generator...