Preface 1Performance Tuning Methodology: A Review Course Structure 1-2 Lesson Objective 1-3 Concepts 1-4 Determining the Worst Bottleneck 1-5 Understanding Workload Characteristics 1-6 A Simple Methodology 1-7 State the Problem 1-9 Find the Problem Stack 1-15 Drill Down and Find the Worst Bottleneck 1-19 Fix It 1-21 Test Against the Baseline 1-22 Repeat Until You Hit Your Goal 1-23 Detecting Performance Problems 1-24 Database Server Stack 1-25 Database Server Tuning 1-26 Summary Enqueue Structures Objectives 2-2 Introduction to Oracle Lock Types 2-3 Enqueues 2-4 Enqueue Identifiers 2-5 Enqueue Modes 2-6 Enqueue Compatibility 2-7 Resources and Locks 2-8 Resource Structure 2-10 Client and Managed Enqueues 2-11 State Objects 2-13 Hashing and Latching 2-14 Resource Free List 2-17 Initialization Parameters 2-18 Lock Acquisition 2-19 Lock Conversion 2-20 Lock Release 2-21 Enqueue Operations 2-22 Enqueue Operations Example 2-23 Wait Event: Enqueue 2-25 Tuning Enqueue Waits 2-27 Deadlock Detection 2-28 Diagnostics: State Object Dump 2-30 Diagnostics: Enqueues Dump 2-34 Diagnostics: V$LOCK 2-36 Diagnostics: V$RESOURCE 2-37 Contents iii

Diagnostics: V$LOCKED_OBJECT 2-38 Diagnostics: Scripts 2-39 Summary 2-41 References Understanding Lock Contention Objectives 3-2 Data Dictionary Locks 3-3 Row Cache Locks 3-4 Wait Event: Row Cache Lock 3-5 Library Cache Locks 3-6 Wait Event: Library Cache Lock 3-7 Library Cache Pins 3-8 Wait Event: Library Cache Pin 3-9 DML Locks 3-10 DML Table Locks: Implementation 3-11 Disabling DML Table Locks 3-12 DML Row Locks 3-14 Row-Level Locks 3-15 Row-Level Conflict 3-16 Resolving Row-Level Conflict 3-18 ITL Contention 3-20 Transaction Locks 3-21 Transaction Identifiers 3-22 Transaction Table Dump 3-24 Finding the Row That Is Locked 3-25 Buffer Locks 3-26 Wait Event: Buffer Busy Waits 3-27 Buffer Lock Contention 3-29 Data Block Contention 3-31 Undo Segment Contention 3-33 Diagnosing Undo Segment Header Contention 3-34 Index Block Contention 3-36 Free List Contention 3-37 Resolving Free List Contention 3-38 Wait Event: Write Complete Waits 3-39 Sort Locks 3-40 ORA SMON Functions 3-42 Coalescing Free Space 3-43 Disabling Background Coalescing 3-44 Temporary Segment Cleanup 3-45 Disabling Temporary Segment Cleanup 3-46 Summary 3-47 References 3-48 iv

4Latch Internals Objectives 4-2 Purpose of Latches 4-3 Latch Characteristics 4-4 Latch Implementation 4-5 Oracle Latch Implementation 4-6 Latch Attributes 4-7 Latch Levels 4-9 Latch Declaration 4-10 Internal Latch Structures 4-11 Latch Interface Routines: Examples 4-12 Waiting for a Latch 4-13 Latch Acquisition in No-Wait Mode 4-15 Latch Acquisition in Wait Mode 4-16 Latch Release 4-18 Latch Cleanup Function 4-19 Wait Event: Latch Free Example 4-20 Using V$ Views 4-30 Latch Contention 4-32 Tuning the Spin Count 4-33 Highly Used Latches 4-34 Diagnostics: Latch Views 4-36 Diagnostics: Latches Dump 4-38 Latch Contention Diagnosis: Example 4-40 Latch Monitoring Summary 4-45 Summary 4-46 Reference Memory Management Objectives 5-2 Memory Areas 5-3 System Global Area 5-4 Dynamic SGA Memory Allocation 5-5 Granule Size 5-7 Granule Memory Manager 5-8 SGA and Shared Memory 5-10 Configuring Shared Memory 5-12 SGA Shared Memory Allocation 5-14 Fixed Area 5-16 Database Block Buffers 5-17 Redo Buffers 5-19 Variable Area 5-20 Heaps and Subheaps 5-21 More on Subheaps 5-22 The Shared Pool 5-23 v

Allocation Classes 5-24 Allocation Classes Viewed in X$KSMSP 5-26 Chunk Allocation: Free Lists 5-27 Chunk Allocation: LRU Lists 5-29 Chunk Allocation: Hidden Free Memory 5-31 The Reserved Pool 5-32 Keeping Objects 5-33 Flushing the Shared Pool 5-34 The Large Pool 5-35 The Java Pool 5-36 Process Global Area 5-37 User Global Area 5-38 Call Global Area 5-39 Heap Dumps 5-40 Subheap Dumps 5-42 Summary 5-43 References The Buffer Cache Objectives 6-2 The Kernel Buffer Cache 6-3 Buffer Cache 6-4 Kernel Layout 6-5 Source Code 6-6 Basic Terminology 6-7 Hash Buckets and Chains 6-8 Overview of Buffer Cache 6-9 Buffer Header (kcbbh) 6-10 Multiple Buffer Pools 6-11 Buffer Pool (kcbwbpd) 6-12 LRU 6-13 Multiple LRU lists 6-14 LRU Lists 6-15 Working Sets (kcbwds) 6-17 Working Sets 6-18 Buffer Cache Users 6-19 Buffer Get 6-20 Buffer Gets 6-21 Getting Current Buffers 6-22 Buffer Management 6-23 Touch Count 6-25 Write Priority 6-27 DBWR and Checkpoints 6-28 Working Sets and DBWR 6-29 DBWR Invocation 6-30 DBWR: Make Clean Buffers 6-31 vi

Checkpoints 6-33 DBWR: LGWR Invocation 6-34 Checkpoint and File Queues 6-35 Checkpoint Queues 6-37 Checkpoint Queue Management 6-38 DBWR: Flush DBA Range 6-39 DBWR: Flush Invalidated Range 6-40 Buffer Cache Events 6-41 Buffer Cache Statistics 6-43 DBWR Statistics 6-45 Buffer Cache Latches 6-46 Buffer Cache Fixed Tables 6-48 Tuning the Buffer Cache 6-49 Buffer Busy Waits 6-51 Free Buffer Waits 6-53 Initialization Parameters 6-54 Additional Tips 6-56 Summary 6-57 References The Library Cache 7-1 Objectives 7-2 The Library Cache 7-3 Library Cache Objects 7-4 Shared Cursors 7-5 Library Cache Architecture 7-7 Hash Buckets 7-8 Object Handles 7-9 Heap 0 (Object) 7-10 Object Types 7-11 Object Names 7-13 Object Flags 7-14 Object Tables 7-16 Object Data Blocks 7-18 Library Cache Object 7-19 Object Heaps 7-20 Locks and Pins 7-22 Lock and Pin Persistence 7-23 Lock Modes 7-24 Lock Compatibility 7-25 Pin Modes 7-26 Library Cache Latches 7-27 Causes of Library Cache Contention 7-29 Sharing Cursors 7-31 Checking for Cursor Sharing 7-32 Diagnostics: V$LIBRARYCACHE 7-34 vii

Diagnostics: Library Cache Dump 7-36 Library Cache Dump Interpretation 7-37 Diagnostics: V$SGASTAT 7-42 Diagnostics: V$SQLAREA 7-44 Other Tuning Tips 7-45 Library Cache Contention Diagnosis 7-47 Latch Contention Diagnostics 7-48 Summary 7-49 References Redo and Archiving 8-1 Objectives 8-2 Redo Architecture Concepts 8-3 Logging Methods 8-4 Oracle9 i Architecture Diagram 8-6 Redo Logging in the Oracle Server 8-7 Page Fix Rule 8-8 Write-Ahead Logging 8-9 Log Force at Commit 8-10 Logical Ordering of Redo 8-11 Redo Log 8-12 Redo Byte Address 8-13 Redo Log Buffer 8-14 Redo Generation 8-16 Writes to Redo Log Files 8-19 LGWR Algorithm 8-21 Redo Wait Events 8-23 Redo Statistics 8-25 Redo Latches 8-27 Optimizing the Redo Buffer 8-28 Tuning Redo Latch Contention 8-30 Redo-less Operations 8-32 NOLOGGING Performance 8-33 Redo with NOLOGGING 8-34 Archiving 8-35 Events that Post the Archiver 8-36 ARCH Process Flow 8-37 Archiver Operations 8-39 Tuning ARCH 8-40 Multiple Archive Log Processes 8-43 Archive Problem Solving 8-44 Summary 8-46 References 8-47 Appendix A Appendix B viii