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Oracle Performance Tuning and Optimization
(Publisher: Macmillan Computer Publishing)
Author(s): Edward Whalen
ISBN: 067230886x
Publication Date: 04/01/96

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Part I
Introduction

Chapter 1 Introduction to Oracle
2 Understanding Terms
3 What Is a Well-Tuned System?
4 Tuning Methodology
5 Benchmarking
6 Performance Monitoring Tools
7 Performance Engineering Starts at the Design Stage

Part I of this book lays down a foundation by presenting an overview of the Oracle architecture and products. In the first few chapters, you gain an understanding of the design of Oracle and the different features available. You also learn what it means to have a well-performing system If you tune a system without having any goals in mind, you usually end in disappointment.

Chapter 4, “Tuning Methodology,” is an overview of my methodology for system performance tuning. This chapter presents the way to plan, execute, and analyze changes and determine what the results mean.

In Chapter 5, “Benchmarking,” you learn how to set up a test to show whether your system is performing well and where the problem areas are. You also learn about some of the industry standard benchmarks and what they mean to you. You are introduced to the Transaction Processing Performance Council (TCP), their Web site, and how you can use the information available.

Chapter 6, “Performance Monitoring Tools,” provides an overview of some of the performance monitoring tools available from Oracle and third-party vendors. The chapter explains how these tools can help you investigate performance problems.

Chapter 7, “Performance Engineering Starts at the Design Stage,” explains the holistic approach to performance engineering. Performance should be engineered into every aspect of the system--from hardware selection and network configuration to database design and application development.

Chapter 1
Introduction to Oracle

To effectively enhance the performance of your Oracle system, it is essential to understand how the product operates. Therefore, I think it appropriate to start this book by reviewing the Oracle architecture. Following the architectural overview, I give an overview of the products and services Oracle provides. This introduction will leave you with an appreciation of the diversity of products Oracle offers.

Oracle Corporation is one of the world’s largest vendors of software for managing information. Oracle has over 12,000 employees with offices in 93 countries around the world. One of the reasons Oracle software is so popular is the diversity of platforms it supports. In fact, Oracle software runs on almost every popular computer in the world and is used everywhere from home applications to giant corporations. Because Oracle is expanding into video, audio, and textual data for consumer applications, the company is poised to become the leading software provider for the Information Superhighway.

Oracle’s products span many areas beyond the core RDBMS with which we are all familiar. Later in this chapter is an overview of some of the many Oracle products and services available, but first let’s look at the core RDBMS.

The Oracle RDBMS (Relational Database Management System) is a product designed to allow simultaneous access into large amounts of stored information. The RDBMS consists of the database (the information) and the instance (the embodiment of the system). The database consists of both the physical files that reside on the system and the logical pieces such as the database schema. These database files take various forms, as described in the following section. The instance is the method used to access the data and consists of processes and system memory.

The Database

The Oracle database has both a logical and a physical layer. The physical layer consists of the actual files that reside on the disk; the components of the logical layer map the data to these physical components.

The Physical Layer

The physical layer of the database consists of three types of files: one or more data files, two or more redo log files, and one or more control files. The data files store the information contained in the database. The redo log files hold information used for recovery in the event of a failure. The control files contain information used to start up an instance, such as the location of data files (see Figure 1.1).


Figure 1.1  The Oracle file structure.

Data Files

The data files contain the information stored in the database. You can have as few as one data file or as many as hundreds of data files. The information for a single table can span many data files or many tables can share a set of data files. Spreading tablespaces over many data files can have a significant positive effect on performance, as discussed in later chapters. The number of data files that can be configured is limited by the Oracle parameter MAXDATAFILES.

Redo Log Files

The redo log files, known collectively as the redo log, store a log of all changes made to the database. This information is used in the event of a system failure to reapply changes that have been made and committed but that may not have been made to the data files. It is essential that the redo log files have good performance and are protected against hardware failures (either through software or hardware fault tolerance). If redo log information is lost, you cannot recover the system.

Control Files

The control files are used to store information such as the locations of data and redo log files; Oracle needs this information to start up the database instance. It is essential that the control files are protected. Oracle provides a mechanism for storing multiple copies of the control files.

The Logical Layer

The logical database consists of the following elements:

  One or more tablespaces.
  The database schema, which consists of items such as tables, clusters, indexes, views, stored procedures, database triggers, sequences, and so on.


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