Oracle® Database
Concepts
10g Release 2 (10.2)
B14220-02
October 2005
Oracle Database Concepts, 10g Release 2 (10.2)
B14220-02
Copyright © 1993, 2005, Oracle. All rights reserved.
Primary Author: Michele Cyran
Contributing Author: Paul Lane, JP Polk
Contributor: Omar Alonso, Penny Avril, Hermann Baer, Sandeepan Banerjee, Mark Bauer, Bill Bridge,
Sandra Cheevers, Carol Colrain, Vira Goorah, Mike Hartstein, John Haydu, Wei Hu, Ramkumar Krishnan,
Vasudha Krishnaswamy, Bill Lee, Bryn Llewellyn, Rich Long, Diana Lorentz, Paul Manning, Valarie Moore,
Mughees Minhas, Gopal Mulagund, Muthu Olagappan, Jennifer Polk, Kathy Rich, John Russell, Viv
Schupmann, Bob Thome, Randy Urbano, Michael Verheij, Ron Weiss, Steve Wertheimer
The Programs (which include both the software and documentation) contain proprietary information; they
are provided under a license agreement containing restrictions on use and disclosure and are also protected
by copyright, patent, and other intellectual and industrial property laws. Reverse engineering, disassembly,
or decompilation of the Programs, except to the extent required to obtain interoperability with other
independently created software or as specified by law, is prohibited.
The information contained in this document is subject to change without notice. If you find any problems in
the documentation, please report them to us in writing. This document is not warranted to be error-free.
Except as may be expressly permitted in your license agreement for these Programs, no part of these
Programs may be reproduced or transmitted in any form or by any means, electronic or mechanical, for any
purpose.
If the Programs are delivered to the United States Government or anyone licensing or using the Programs on
behalf of the United States Government, the following notice is applicable:
U.S. GOVERNMENT RIGHTS Programs, software, databases, and related documentation and technical data
delivered to U.S. Government customers are "commercial computer software" or "commercial technical data"
pursuant to the applicable Federal Acquisition Regulation and agency-specific supplemental regulations. As
such, use, duplication, disclosure, modification, and adaptation of the Programs, including documentation
and technical data, shall be subject to the licensing restrictions set forth in the applicable Oracle license
agreement, and, to the extent applicable, the additional rights set forth in FAR 52.227-19, Commercial
Computer Software—Restricted Rights (June 1987). Oracle Corporation, 500 Oracle Parkway, Redwood City,
CA 94065
The Programs are not intended for use in any nuclear, aviation, mass transit, medical, or other inherently
dangerous applications. It shall be the licensee's responsibility to take all appropriate fail-safe, backup,
redundancy and other measures to ensure the safe use of such applications if the Programs are used for such
purposes, and we disclaim liability for any damages caused by such use of the Programs.
Oracle, JD Edwards, PeopleSoft, and Retek are registered trademarks of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective owners.
The Programs may provide links to Web sites and access to content, products, and services from third
parties. Oracle is not responsible for the availability of, or any content provided on, third-party Web sites.
You bear all risks associated with the use of such content. If you choose to purchase any products or services
from a third party, the relationship is directly between you and the third party. Oracle is not responsible for:
(a) the quality of third-party products or services; or (b) fulfilling any of the terms of the agreement with the
third party, including delivery of products or services and warranty obligations related to purchased
products or services. Oracle is not responsible for any loss or damage of any sort that you may incur from
dealing with any third party.
iii
Contents
Preface ............................................................................................................................................................. xxv
Audience................................................................................................................................................... xxv
Documentation Accessibility................................................................................................................. xxv
Related Documentation.......................................................................................................................... xxvi
Conventions ............................................................................................................................................. xxvi
Part I What Is Oracle?
1 Introduction to the Oracle Database
Oracle Database Architecture ............................................................................................................... 1-1
Overview of Oracle Grid Architecture............................................................................................ 1-2
Grid Computing Defined........................................................................................................... 1-2
Grid Computing in Oracle Database 10g................................................................................. 1-5
Overview of Application Architecture ........................................................................................... 1-7
Client/Server Architecture........................................................................................................ 1-7
Multitier Architecture: Application Servers ........................................................................... 1-7
Overview of Physical Database Structures..................................................................................... 1-8
Datafiles ....................................................................................................................................... 1-8
Control Files................................................................................................................................. 1-8
Redo Log Files ............................................................................................................................. 1-9
Archive Log Files ........................................................................................................................ 1-9
Parameter Files............................................................................................................................ 1-9
Alert and Trace Log Files........................................................................................................... 1-9
Backup Files.............................................................................................................................. 1-10
Overview of Logical Database Structures ................................................................................... 1-10
Tablespaces ............................................................................................................................... 1-10
Oracle Data Blocks................................................................................................................... 1-10
Extents ....................................................................................................................................... 1-11
Segments ................................................................................................................................... 1-11
Overview of Schemas and Common Schema Objects ............................................................... 1-12
Tables......................................................................................................................................... 1-12
Indexes ...................................................................................................................................... 1-12
Views ......................................................................................................................................... 1-12
Clusters...................................................................................................................................... 1-13
Synonyms.................................................................................................................................. 1-13
iv
Overview of the Oracle Data Dictionary ..................................................................................... 1-13
Overview of the Oracle Instance................................................................................................... 1-13
Real Application Clusters: Multiple Instance Systems....................................................... 1-13
Instance Memory Structures ................................................................................................. 1-14
System Global Area ................................................................................................................. 1-14
Program Global Area............................................................................................................... 1-15
Oracle Background Processes ................................................................................................ 1-15
Process Architecture................................................................................................................ 1-15
Overview of Accessing the Database........................................................................................... 1-16
Network Connections.............................................................................................................. 1-16
Starting Up the Database ........................................................................................................ 1-16
How Oracle Works ................................................................................................................. 1-17
Overview of Oracle Utilities.......................................................................................................... 1-17
Oracle Database Features .................................................................................................................... 1-17
Overview of Scalability and Performance Features................................................................... 1-18
Concurrency ............................................................................................................................. 1-18
Read Consistency .................................................................................................................... 1-18
Locking Mechanisms .............................................................................................................. 1-19
Quiesce Database ..................................................................................................................... 1-20
Real Application Clusters....................................................................................................... 1-20
Portability.................................................................................................................................. 1-20
Overview of Manageability Features........................................................................................... 1-21
Self-Managing Database ......................................................................................................... 1-21
Oracle Enterprise Manager..................................................................................................... 1-21
SQL*Plus.................................................................................................................................... 1-21
Automatic Storage Management........................................................................................... 1-21
The Scheduler ........................................................................................................................... 1-22
Database Resource Manager ................................................................................................. 1-22
Overview of Database Backup and Recovery Features............................................................. 1-22
Types of Failures ..................................................................................................................... 1-22
Structures Used for Recovery ................................................................................................ 1-23
Overview of High Availability Features...................................................................................... 1-24
Overview of Business Intelligence Features................................................................................ 1-25
Data Warehousing ................................................................................................................... 1-25
Extraction, Transformation, and Loading (ETL)................................................................. 1-25
Materialized Views.................................................................................................................. 1-25
Bitmap Indexes in Data Warehousing .................................................................................. 1-26
Table Compression .................................................................................................................. 1-26
Parallel Execution .................................................................................................................... 1-26
Analytic SQL............................................................................................................................. 1-26
OLAP Capabilities ................................................................................................................... 1-26
Data Mining.............................................................................................................................. 1-27
Partitioning ............................................................................................................................... 1-27
Overview of Content Management Features.............................................................................. 1-27
XML in Oracle........................................................................................................................... 1-27
LOBs........................................................................................................................................... 1-27
Oracle Text ............................................................................................................................... 1-28
v
Oracle Ultra Search ................................................................................................................. 1-28
Oracle interMedia..................................................................................................................... 1-28
Oracle Spatial............................................................................................................................ 1-28
Overview of Security Features...................................................................................................... 1-28
Security Mechanisms .............................................................................................................. 1-29
Overview of Data Integrity and Triggers.................................................................................... 1-29
Integrity Constraints................................................................................................................ 1-30
Keys ........................................................................................................................................... 1-30
Triggers ..................................................................................................................................... 1-30
Overview of Information Integration Features........................................................................... 1-31
Distributed SQL ...................................................................................................................... 1-31
Oracle Streams ......................................................................................................................... 1-31
Oracle Transparent Gateways and Generic Connectivity ................................................. 1-33
Oracle Database Application Development ................................................................................... 1-33
Overview of Oracle SQL ................................................................................................................ 1-33
SQL Statements ........................................................................................................................ 1-33
Overview of PL/SQL...................................................................................................................... 1-34
PL/SQL Program Units .......................................................................................................... 1-35
Overview of Java............................................................................................................................. 1-35
Overview of Application Programming Languages (APIs) ..................................................... 1-35
Overview of Transactions.............................................................................................................. 1-36
Commit and Undo Transactions............................................................................................ 1-37
Savepoints ................................................................................................................................. 1-37
Overview of Datatypes................................................................................................................... 1-37
Overview of Globalization ............................................................................................................ 1-38
Part II Oracle Database Architecture
2 Data Blocks, Extents, and Segments
Introduction to Data Blocks, Extents, and Segments ........................................................................ 2-1
Overview of Data Blocks ........................................................................................................................ 2-3
Data Block Format ............................................................................................................................. 2-3
Header (Common and Variable) .............................................................................................. 2-4
Table Directory............................................................................................................................ 2-4
Row Directory ............................................................................................................................. 2-4
Overhead...................................................................................................................................... 2-4
Row Data...................................................................................................................................... 2-4
Free Space..................................................................................................................................... 2-4
Free Space Management.................................................................................................................... 2-4
Availability and Optimization of Free Space in a Data Block.............................................. 2-5
Row Chaining and Migrating .................................................................................................. 2-5
PCTFREE, PCTUSED, and Row Chaining .................................................................................... 2-6
The PCTFREE Parameter........................................................................................................... 2-6
The PCTUSED Parameter.......................................................................................................... 2-7
Overview of Extents.............................................................................................................................. 2-10
When Extents Are Allocated ........................................................................................................ 2-10
