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

Detecting and preventing lock contention


If databases were used by a single user there would be no need for locks, because other users are not accessing the same data at the same time. In this recipe we will see how two concurrent sessions experience wait time due to locks, and how to diagnose them and what to do to resolve and avoid these situations.

Getting ready

In this recipe we use three concurrent SQL*Plus sessions to simulate two concurrent users in the first two sessions, while querying dynamic performance views in a third session. We will use the TESTDB database in the rest of this book.

How to do it...

The following steps will show how to detect and prevent lock contention:

  1. Connect SESSION1 as user SH:

    -- SESSION 1
    CONNECT sh@TESTDB/sh
    
  2. Update a row in SESSION1, not completing the transaction with a COMMIT or ROLLBACK statement:

    UPDATE CUSTOMERS SET
      CUST_FIRST_NAME = 'TEST1'
      WHERE CUST_ID = 26;
    
  3. Connect SESSION2 as user SH:

    -- SESSION 2
    CONNECT sh@TESTDB/sh
    
  4. Update the same row SESSION2...