Expert.oracle.database.architecture.2nd.edition

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Expert.oracle.database.architecture.2nd.edition

  1. 1. THE EXPERT’S VOICE ® IN ORACLEExpertOracleDatabase ArchitectureOracle Database 9i, 10g, and 11gProgramming Techniques and SolutionsSECOND EDITIONThomas KyteForewords by Jonathan Lewis and Ken Jacobs (aka “Dr. DBA”)
  2. 2. Praise forExpert Oracle Database Architecture:9i and 10g Programming Techniques and Solutions “This book will help you make the best use of Oracle technology. Emulating Tom’s rational methodology, and demand for proof by example, will make you a far better technology thinker. Without question, this is one of the most important Oracle books you can possess.” —Ken Jacobs, (aka “Dr. DBA”) Vice President of Product Strategy (Server Technologies), Oracle Corporation “It’s an excellent book, full of plenty of deep insights about Oracle technology.” —Sean Hull, Heavyweight Internet Group (http://iheavy.com)
  3. 3. Expert Oracle Database ArchitectureOracle Database 9i, 10g, and 11g Programming Techniques and Solutions Second Edition■■■Thomas Kyte
  4. 4. Expert Oracle Database Architecture: Oracle Database 9i, 10g, and 11g ProgrammingTechniques and Solutions, Second EditionCopyright © 2010 by Thomas KyteAll rights reserved. No part of this work may be reproduced or transmitted in any form or by any means,electronic or mechanical, including photocopying, recording, or by any information storage or retrievalsystem, without the prior written permission of the copyright owner and the publisher.ISBN-13 (pbk): 978-1-4302-2946-9ISBN-13 (electronic): 978-1-4302-2947-6Printed and bound in the United States of America 9 8 7 6 5 4 3 2 1Trademarked names, logos, and images may appear in this book. Rather than use a trademark symbolwith every occurrence of a trademarked name, logo, or image we use the names, logos, and images onlyin an editorial fashion and to the benefit of the trademark owner, with no intention of infringement ofthe trademark.The use in this publication of trade names, trademarks, service marks, and similar terms, even if they arenot identified as such, are not to be taken as an expression of opinion as to whether or not they aresubject to proprietary rights. President and Publisher: Paul Manning Lead Editor: Jonathan Gennick Technical Reviewers: Christopher Beck, Melanie Caffrey, and Jason Straub Editorial Board: Clay Andres, Steve Anglin, Mark Beckner, Ewan Buckingham, Gary Cornell, Jonathan Gennick, Jonathan Hassell, Michelle Lowman, Matthew Moodie, Duncan Parkes, Jeffrey Pepper, Frank Pohlmann, Douglas Pundick, Ben Renow-Clarke, Dominic Shakeshaft, Matt Wade, Tom Welsh Coordinating Editor: Debra Kelly Copy Editors: Mary Behr and Sharon Terdeman Compositor: Mary Sudul Indexer: BIM Indexing and Proofreading Services Artist: April Milne Cover Designer: Anna IshchenkoDistributed to the book trade worldwide by Springer Science+Business Media, LLC., 233 SpringStreet, 6th Floor, New York, NY 10013. Phone 1-800-SPRINGER, fax (201) 348-4505, e-mailorders-ny@springer-sbm.com, or visit www.springeronline.com.For information on translations, please e-mail rights@apress.com, or visit www.apress.com.Apress and friends of ED books may be purchased in bulk for academic, corporate, or promotional use.eBook versions and licenses are also available for most titles. For more information, reference ourSpecial Bulk Sales–eBook Licensing web page at www.apress.com/info/bulksales.The information in this book is distributed on an “as is” basis, without warranty. Although everyprecaution has been taken in the preparation of this work, neither the author(s) nor Apress shall haveany liability to any person or entity with respect to any loss or damage caused or alleged to be causeddirectly or indirectly by the information contained in this work.The source code for this book is available to readers at www.apress.com.
  5. 5. Contents at a Glance ■ Chapter 1: Developing Successful Oracle Applications .......................................1 ■ Chapter 2: Architecture Overview......................................................................51 ■ Chapter 3: Files ..................................................................................................67 ■ Chapter 4: Memory Structures.........................................................................121 ■ Chapter 5: Oracle Processes............................................................................165 ■ Chapter 6: Locking and Latching .....................................................................195 ■ Chapter 7: Concurrency and Multi-versioning .................................................243 ■ Chapter 8: Transactions...................................................................................267 ■ Chapter 9: Redo and Undo................................................................................299 ■ Chapter 10: Database Tables ...........................................................................345 ■ Chapter 11: Indexes .........................................................................................425 ■ Chapter 12: Datatypes......................................................................................493 ■ Chapter 13: Partitioning...................................................................................557 ■ Chapter 14: Parallel Execution.........................................................................621 ■ Chapter 15: Data Loading and Unloading.........................................................657 ■ Chapter 16: Data Encryption ............................................................................709 Index.....................................................................................................................751 v
  6. 6. ■ CONTENTS Contents Contents at a Glance.................................................................................................v Foreword ............................................................................................................. xviii Foreword from the First Edition ............................................................................ xix About the Author .................................................................................................. xxii About the Technical Reviewers ........................................................................... xxiii Acknowledgments ............................................................................................... xxiv Introduction .......................................................................................................... xxv Setting Up Your Environment ............................................................................. xxxii ■ Chapter 1: Developing Successful Oracle Applications .......................................1 My Approach....................................................................................................................2 The Black Box Approach..................................................................................................3 How (and How Not) to Develop Database Applications .................................................11 Understanding Oracle Architecture ......................................................................................................12 Understanding Concurrency Control.....................................................................................................21 Multi-Versioning ...................................................................................................................................25 Database Independence? .....................................................................................................................32 How Do I Make It Run Faster? ..............................................................................................................46 The DBA-Developer Relationship..........................................................................................................48 Summary .......................................................................................................................49vi
  7. 7. ■ CONTENTS■ Chapter 2: Architecture Overview......................................................................51 Defining Database and Instance....................................................................................52 The SGA and Background Processes....................................................................................................58 Connecting to Oracle .....................................................................................................60 Dedicated Server ..................................................................................................................................60 Shared Server.......................................................................................................................................62 Mechanics of Connecting over TCP/IP..................................................................................................63 Summary .......................................................................................................................66■ Chapter 3: Files ..................................................................................................67 Parameter Files..............................................................................................................68 What Are Parameters?..........................................................................................................................69 Legacy init.ora Parameter Files............................................................................................................73 Server Parameter Files (SPFILEs) ..................................................................................74 Converting to SPFILEs ..........................................................................................................................75 Trace Files .....................................................................................................................82 Requested Trace Files ..........................................................................................................................83 Trace Files Generated in Response to Internal Errors ..........................................................................88 Trace File Wrap-up ...............................................................................................................................93 Alert File ........................................................................................................................93 Data Files.......................................................................................................................96 A Brief Review of File System Mechanisms .........................................................................................96 The Storage Hierarchy in an Oracle Database......................................................................................97 Dictionary-Managed and Locally-Managed Tablespaces...................................................................101 Temp Files ...................................................................................................................103 Control Files.................................................................................................................105 Redo Log Files .............................................................................................................105 Online Redo Log..................................................................................................................................106 Archived Redo Log..............................................................................................................................108 Password Files.............................................................................................................109 vii
  8. 8. ■ CONTENTS Change Tracking File ...................................................................................................113 Flashback Logs............................................................................................................114 Flashback Database ...........................................................................................................................114 Flash Recovery Area...........................................................................................................................115 DMP Files (EXP/IMP Files)............................................................................................116 Data Pump Files...........................................................................................................117 Flat Files ......................................................................................................................120 Summary .....................................................................................................................120 ■ Chapter 4: Memory Structures.........................................................................121 The Process Global Area and User Global Area ...........................................................122 Manual PGA Memory Management ....................................................................................................123 Automatic PGA Memory Management................................................................................................129 Choosing Between Manual and Auto Memory Management..............................................................140 PGA and UGA Wrap-up........................................................................................................................142 The System Global Area...............................................................................................142 Fixed SGA ...........................................................................................................................................148 Redo Buffer.........................................................................................................................................148 Block Buffer Cache .............................................................................................................................149 Shared Pool ........................................................................................................................................156 Large Pool...........................................................................................................................................159 Java Pool ............................................................................................................................................160 Streams Pool ......................................................................................................................................160 Automatic SGA Memory Management................................................................................................161 Automatic Memory Management .......................................................................................................162 Summary .....................................................................................................................164 ■ Chapter 5: Oracle Processes............................................................................165 Server Processes.........................................................................................................166 Dedicated Server Connections ...........................................................................................................166 Shared Server Connections ................................................................................................................169viii
  9. 9. ■ CONTENTS Database Resident Connection Pooling (DRCP) ..................................................................................170 Connections vs. Sessions ...................................................................................................................170 Dedicated Server vs. Shared Server vs. DRCP ...................................................................................176 Dedicated/Shared Server Wrap-up.....................................................................................................179 Background Processes ................................................................................................180 Focused Background Processes.........................................................................................................181 Utility Background Processes.............................................................................................................190 Slave Processes...........................................................................................................193 I/O Slaves............................................................................................................................................193 Pnnn: Parallel Query Execution Servers .............................................................................................193 Summary .....................................................................................................................194■ Chapter 6: Locking and Latching .....................................................................195 What Are Locks?..........................................................................................................195 Locking Issues .............................................................................................................198 Lost Updates.......................................................................................................................................198 Pessimistic Locking............................................................................................................................199 Optimistic Locking ..............................................................................................................................201 Optimistic or Pessimistic Locking?.....................................................................................................207 Blocking..............................................................................................................................................208 Deadlocks ...........................................................................................................................................211 Lock Escalation...................................................................................................................................215 Lock Types...................................................................................................................216 DML Locks ..........................................................................................................................................216 DDL Locks...........................................................................................................................................225 Latches ...............................................................................................................................................230 Mutexes ..............................................................................................................................................240 Manual Locking and User-Defined Locks ...........................................................................................240 Summary .....................................................................................................................241 ix
  10. 10. ■ CONTENTS ■ Chapter 7: Concurrency and Multi-versioning .................................................243 What Are Concurrency Controls?.................................................................................243 Transaction Isolation Levels ........................................................................................244 READ UNCOMMITTED..........................................................................................................................246 READ COMMITTED ..............................................................................................................................248 REPEATABLE READ .............................................................................................................................249 SERIALIZABLE .....................................................................................................................................252 READ ONLY .........................................................................................................................................254 Implications of Multi-version Read Consistency..........................................................255 A Common Data Warehousing Technique That Fails..........................................................................255 An Explanation for Higher Than Expected I/O on Hot Tables ..............................................................256 Write Consistency ........................................................................................................259 Consistent Reads and Current Reads .................................................................................................259 Seeing a Restart .................................................................................................................................262 Why Is a Restart Important to Us? ......................................................................................................264 Summary .....................................................................................................................265 ■ Chapter 8: Transactions...................................................................................267 Transaction Control Statements ..................................................................................267 Atomicity......................................................................................................................269 Statement-Level Atomicity .................................................................................................................269 Procedure-Level Atomicity .................................................................................................................271 Transaction-Level Atomicity ...............................................................................................................275 DDL and Atomicity ..............................................................................................................................275 Durability .....................................................................................................................275 WRITE Extensions to COMMIT.............................................................................................................276 COMMITS in a Non-Distributed PL/SQL Block ....................................................................................277 Integrity Constraints and Transactions........................................................................279 IMMEDIATE Constraints ......................................................................................................................279 DEFERRABLE Constraints and Cascading Updates.............................................................................280x
  11. 11. ■ CONTENTS Bad Transaction Habits................................................................................................284 Committing in a Loop .........................................................................................................................284 Using Autocommit ..............................................................................................................................290 Distributed Transactions..............................................................................................291 Autonomous Transactions ...........................................................................................293 How Autonomous Transactions Work.................................................................................................293 When to Use Autonomous Transactions .............................................................................................295 Summary .....................................................................................................................298■ Chapter 9: Redo and Undo................................................................................299 What Is Redo?..............................................................................................................300 What Is Undo?..............................................................................................................300 How Redo and Undo Work Together............................................................................304 Example INSERT-UPDATE-DELETE Scenario ......................................................................................304 Commit and Rollback Processing ................................................................................308 What Does a COMMIT Do? ..................................................................................................................308 What Does a ROLLBACK Do? ..............................................................................................................315 Investigating Redo .......................................................................................................316 Measuring Redo..................................................................................................................................316 Can I Turn Off Redo Log Generation? .................................................................................................318 Why Can’t I Allocate a New Log?........................................................................................................321 Block Cleanout....................................................................................................................................323 Log Contention....................................................................................................................................326 Temporary Tables and Redo/Undo .....................................................................................................328 Investigating Undo .......................................................................................................332 What Generates the Most and Least Undo? .......................................................................................332 ORA-01555: snapshot too old Error ....................................................................................................334 Summary .....................................................................................................................344 xi
  12. 12. ■ CONTENTS ■ Chapter 10: Database Tables ...........................................................................345 Types of Tables............................................................................................................345 Terminology .................................................................................................................347 Segment .............................................................................................................................................347 Segment Space Management ............................................................................................................350 High-water Mark ................................................................................................................................350 FREELISTS ..........................................................................................................................................352 PCTFREE and PCTUSED ......................................................................................................................356 LOGGING and NOLOGGING ..................................................................................................................359 INITRANS and MAXTRANS ..................................................................................................................359 Heap Organized Tables................................................................................................359 Index Organized Tables ...............................................................................................363 Index Organized Tables Wrap-up .......................................................................................................378 Index Clustered Tables ................................................................................................378 Index Clustered Tables Wrap-up ........................................................................................................386 Hash Clustered Tables .................................................................................................386 Hash Clustered Tables Wrap-up .........................................................................................................394 Sorted Hash Clustered Tables .....................................................................................395 Nested Tables ..............................................................................................................397 Nested Tables Syntax .........................................................................................................................398 Nested Table Storage .........................................................................................................................405 Nested Tables Wrap-up ......................................................................................................................408 Temporary Tables ........................................................................................................409 Temporary Tables Wrap-up ................................................................................................................415 Object Tables ...............................................................................................................416 Object Tables Wrap-up .......................................................................................................................423 Summary .....................................................................................................................423xii
  13. 13. ■ CONTENTS■ Chapter 11: Indexes .........................................................................................425 An Overview of Oracle Indexes ....................................................................................425 B*Tree Indexes ............................................................................................................427 Index Key Compression ......................................................................................................................430 Reverse Key Indexes ..........................................................................................................................433 Descending Indexes ...........................................................................................................................439 When Should You Use a B*Tree Index? ..............................................................................................441 B*Trees Wrap-up ................................................................................................................................452 Bitmap Indexes ............................................................................................................452 When Should You Use a Bitmap Index?..............................................................................................453 Bitmap Join Indexes ...........................................................................................................................457 Bitmap Indexes Wrap-up ....................................................................................................................459 Function-Based Indexes ..............................................................................................460 Important Implementation Details ......................................................................................................460 A Simple Function-Based Index Example...........................................................................................461 Indexing Only Some of the Rows........................................................................................................470 Implementing Selective Uniqueness ..................................................................................................472 Caveat Regarding ORA-01743 ............................................................................................................472 Function-Based Indexes Wrap-up ......................................................................................................473 Application Domain Indexes ........................................................................................474 Frequently Asked Questions and Myths About Indexes...............................................475 Do Indexes Work on Views? ...............................................................................................................475 Do Nulls and Indexes Work Together?................................................................................................475 Should Foreign Keys Be Indexed? ......................................................................................................477 Why Isn’t My Index Getting Used? ......................................................................................................479 Myth: Space Is Never Reused in an Index ..........................................................................................485 Myth: Most Discriminating Elements Should Be First ........................................................................488 Summary .....................................................................................................................491 xiii
  14. 14. ■ CONTENTS ■ Chapter 12: Datatypes......................................................................................493 An Overview of Oracle Datatypes ................................................................................493 Character and Binary String Types ..............................................................................496 NLS Overview .....................................................................................................................................496 Character Strings................................................................................................................................499 Binary Strings: RAW Types ..........................................................................................506 Number Types..............................................................................................................508 NUMBER Type Syntax and Usage .......................................................................................................510 BINARY_FLOAT/BINARY_DOUBLE Type Syntax and Usage.................................................................513 Non-native Number Types..................................................................................................................514 Performance Considerations ..............................................................................................................514 Long Types ..................................................................................................................516 Restrictions on LONG and LONG RAW Types ......................................................................................516 Coping with Legacy LONG Types ........................................................................................................518 Dates, Timestamps, and Interval Types.......................................................................523 Formats ..............................................................................................................................................523 DATE Type ..........................................................................................................................................525 TIMESTAMP Type................................................................................................................................531 INTERVAL Type ...................................................................................................................................538 LOB Types....................................................................................................................541 Internal LOBs ......................................................................................................................................541 BFILEs.................................................................................................................................................552 ROWID/UROWID Types .................................................................................................554 Summary .....................................................................................................................555 ■ Chapter 13: Partitioning...................................................................................557 Partitioning Overview ..................................................................................................557 Increased Availability .........................................................................................................................558 Reduced Administrative Burden .........................................................................................................560 Enhanced Statement Performance.....................................................................................................564xiv
  15. 15. ■ CONTENTS Table Partitioning Schemes.........................................................................................566 Range Partitioning ..............................................................................................................................567 Hash Partitioning ................................................................................................................................569 List Partitioning ..................................................................................................................................574 Interval Partitioning ............................................................................................................................575 Reference Partitioning........................................................................................................................581 Composite Partitioning .......................................................................................................................586 Row Movement...................................................................................................................................588 Table Partitioning Schemes Wrap-up .................................................................................................590 Partitioning Indexes .....................................................................................................591 Local Indexes vs. Global Indexes........................................................................................................592 Local Indexes......................................................................................................................................593 Global Indexes ....................................................................................................................................599 Partitioning and Performance, Revisited .....................................................................612 Auditing and Segment Space Compression.................................................................618 Summary .....................................................................................................................619■ Chapter 14: Parallel Execution.........................................................................621 When to Use Parallel Execution ...................................................................................622 A Parallel Processing Analogy ............................................................................................................623 Oracle Exadata.............................................................................................................624 Parallel Query ..............................................................................................................624 Parallel DML.................................................................................................................630 Parallel DDL .................................................................................................................633 Parallel DDL and Data Loading Using External Tables........................................................................634 Parallel DDL and Extent Trimming......................................................................................................636 Parallel Recovery .........................................................................................................645 Procedural Parallelism.................................................................................................645 Parallel Pipelined Functions ...............................................................................................................646 Do-It-Yourself Parallelism ..................................................................................................................649 xv
  16. 16. ■ CONTENTS Old School Do-It-Yourself Parallelism ................................................................................................652 Summary .....................................................................................................................656 ■ Chapter 15: Data Loading and Unloading.........................................................657 SQL*Loader..................................................................................................................657 Loading Data with SQLLDR FAQs........................................................................................................661 SQLLDR Caveats .................................................................................................................................686 SQLLDR Summary ..............................................................................................................................686 External Tables .................................................................................