Expert Oracle Database Architecture Oracle Database 9/, Techniques and Solutions 10gr, and 11g Programming Second Edition TECHNiSCHE JNFORMATIONSBIBLIOTHEK UN!VERSITAT BIBLIOTHEK HANNOVER Thomas Kyte Apress
Contents Contents at a Glance Foreword Foreword from the First Edition About the Author About the Technical Reviewers Acknowledgments Introduction. Setting Up Your Environment v xviii xix xxii xxiii xxiv».xxv 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 49 vi
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
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 169 viii
II 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
Chapter 7: Concurrency and Mutti-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 280 x
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 0RA-01555: snapshot too old Error 334 Summary 344 xi
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 423 xii
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
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 564 xiv
11 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
m CONTENTS Old School Do-It-Yourself Parallelism 652 Summary 656 Chapter 15: Data Loading and Unloading 657 SQIAoader. 657 Loading Data with SQLLDR FAQs 661 SQLLDR Caveats 686 SQLLDR Summary 686 External Tables 686 Setting Up External Tables 687 Dealing with Errors 693 Using an External Table to Load Different Files 696 Multiuser Issues 696 External Tables Summary 697 Flat File Unload - 698 Data Pump Unload 706 Summary 708 Chapter 16: Data Encryption...709 Types of Encryption 709 Data in Motion 709 Data at Rest 710 Manual Application Encryption 713 The Oracle Wallet 714 Transparent Column Level Encryption 717 Transparent Tablespace Encryption 719 What Encryption Is Not About 722 Implementing Manual Application Encryption 723 Reasons to Avoid the Manual Approach 723 Performance Implications of the Manual Approach 724 When to Use the Manual Approach 729 xvi
Implementing Column Level Encryption 729 How to Use Column Encryption 729 Data Storage with Column Encryption 730 Measuring the Performance Impact of Column Encryption, 734 Influences on the Magnitude 734 Limitations of Column Encryption 740 Implementing Tablespace Encryption 741 How to Use Tablespace Encryption 741 Data Storage with Tablespace Encryption 741 Measuring the Performance Impact of Tablespace Encryption 743 Deciding on an Encryption Technique 748 Summary 749 Index - 751 xvii