Oracle9i Database: Advanced Instance Tuning

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1 Oracle9i Database: Advanced Instance Tuning Student Guide D16442GC10 Edition 1.0 December 2002 D37574

2 Authors Lex de Haan Joel Goodman Technical Contributors and Reviewers Scott Gossett Christine Jeal Richard Powell Harald van Breederode Jim Womack Publisher John B Dawson Copyright Oracle Corporation, All rights reserved. This documentation contains proprietary information of Oracle Corporation. It is provided under a license agreement containing restrictions on use and disclosure and is also protected by copyright law. Reverse engineering of the software is prohibited. If this documentation is delivered to a U.S. Government Agency of the Department of Defense, then it is delivered with Restricted Rights and the following legend is applicable: Restricted Rights Legend Use, duplication or disclosure by the Government is subject to restrictions for commercial computer software and shall be deemed to be Restricted Rights software under Federal law, as set forth in subparagraph (c)(1)(ii) of DFARS , Rights in Technical Data and Computer Software (October 1988). This material or any portion of it may not be copied in any form or by any means without the express prior written permission of Oracle Corporation. Any other copying is a violation of copyright law and may result in civil and/or criminal penalties. If this documentation is delivered to a U.S. Government Agency not within the Department of Defense, then it is delivered with Restricted Rights, as defined in FAR , Rights in Data-General, including Alternate III (June 1987). The information in this document is subject to change without notice. If you find any problems in the documentation, please report them in writing to Education Products, Oracle Corporation, 500 Oracle Parkway, Box SB-6, Redwood Shores, CA Oracle Corporation does not warrant that this document is error-free. SQL, PL/SQL, Oracle DBMS, Oracle Universal Data Server, Oracle Application Server, LiveHTML are trademarks or registered trademarks of Oracle Corporation. All other products or company names are used for identification purposes only, and may be trademarks of their respective owners.

3 Contents I Oracle9i Database: Advanced Instance Tuning Seminar Series Overview I-2 Lesson Overview I-3 Disclaimer I-4 1 Performance Tuning Methodology Objectives 1-2 Concepts 1-3 Understanding Workload Characteristics 1-4 A Simple Methodology State the Problem Find the Problem Stack Drill Down and Find the Worst Bottleneck Fix It Test Against the Baseline Repeat Until You Hit Your Goal 1-13 Database Server Stack 1-14 Database Server Tuning 1-15 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 and Lock Structures 2-9 Client and Managed Enqueues 2-10 State Objects 2-11 Hashing and Latching 2-12 Resource Freelist 2-15 Initialization Parameters 2-16 Lock Acquisition 2-17 Lock Conversion 2-18 Lock Release 2-19 Enqueue Operations 2-20 Enqueue Operations Example 2-21 Wait Event: Enqueue 2-23 Tuning Enqueue Waits 2-25 iii

4 Deadlock Detection 2-26 Diagnostics: V$LOCK 2-28 Diagnostics: V$RESOURCE 2-29 Diagnostics: V$LOCKED_OBJECT 2-30 Diagnostics: Scripts 2-31 Summary 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 3-13 Row Level Locks 3-14 Row Level Conflict 3-15 Transaction Locks 3-16 Transaction Identifiers 3-17 Buffer Locks 3-18 Wait Event: Buffer Busy Waits 3-19 Data Block Contention 3-20 Undo Segment Contention 3-21 Index Block Contention 3-22 Free List Contention 3-23 Resolving Free List Contention 3-24 Wait Event: Write Complete Waits 3-25 ORA SMON Functions 3-27 Coalescing Free Space 3-28 Disabling Background Coalescing 3-29 Temporary Segment Cleanup 3-30 Disabling Temporary Segment Cleanup 3-31 Summary 3-32 iv

5 4 Latch Internals Objectives 4-2 Purpose of Latches 4-3 Latch Characteristics 4-4 Latch Implementation 4-5 Latch Attributes 4-6 Waiting for a Latch 4-7 Latch Acquisition in No-Wait Mode 4-8 Latch Acquisition in Wait Mode 4-9 Latch Release 4-10 Latch Cleanup Function 4-11 Wait Event: Latch Free Example 4-12 Using V$ Views 4-18 Latch Contention 4-20 Highly Used Latches 4-21 Diagnostics: Latch Views 4-23 Latch Contention Diagnosis: Example 4-24 Summary Memory Management Objectives 5-2 Oracle Server Memory Areas 5-3 SGA Components 5-4 Dynamic SGA Memory Allocation 5-5 Fixed Area 5-6 Database Block Buffers 5-7 Redo Buffers 5-8 Variable Area 5-9 Heaps and Subheaps 5-10 The Shared Pool 5-11 Allocation Classes 5-12 Chunk Allocation: Free Lists 5-13 Chunk Allocation: LRU Lists 5-14 Chunk Allocation: Hidden Free Memory 5-15 The Reserved Pool 5-16 Keeping Objects 5-17 Flushing the Shared Pool 5-18 The Large Pool 5-19 The Java Pool 5-20 v

6 Process Global Area (PGA) 5-21 User Global Area (UGA) 5-22 Call Global Area (CGA) 5-23 Summary The Buffer Cache Objectives 6-2 Buffer Cache 6-3 Basic Terminology 6-4 Hash Buckets and Chains 6-5 Overview of Buffer Cache 6-6 LRU Lists 6-7 Working Sets 6-8 Buffer Management 6-9 Buffer Gets 6-11 Getting Current Buffers 6-12 Write Priority 6-13 DBWR Invocation 6-14 DBWR: Make Clean Buffers 6-15 Checkpoints 6-16 Checkpoint and File Queues 6-17 Checkpoint Queues 6-19 Checkpoint Queue Management 6-20 DBWR: Flush DBA Range 6-21 DBWR: Flush Invalidated Range 6-22 Buffer Cache Events 6-23 Buffer Busy Waits 6-24 Buffer Cache Statistics 6-25 DBWR Statistics 6-26 Buffer Cache Latches 6-27 Buffer Cache Fixed Tables and Views 6-28 Tuning the Buffer Cache 6-29 Hidden Parameters: Some Examples 6-30 Summary The Library Cache Objectives 7-2 The Library Cache 7-3 Library Cache Objects 7-4 Shared Cursors 7-5 vi

7 Library Cache Architecture 7-7 Hash Buckets 7-8 Object Handles 7-9 Object Types 7-10 Object Names 7-11 Object Flags 7-12 Object Tables 7-13 Object Data Blocks 7-14 Locks and Pins 7-15 Lock Modes 7-16 Lock Compatibility 7-17 Pin Modes 7-18 Library Cache Latches 7-19 Causes of Library Cache Contention 7-21 Sharing Cursors 7-23 Diagnostics: V$LIBRARYCACHE 7-24 Diagnostics: V$SGASTAT 7-25 Diagnostics: V$SQLAREA 7-26 Library Cache Contention Diagnosis 7-27 Latch Contention Diagnostics 7-28 Summary Redo and Archiving Objectives 8-2 Redo Logging in the Oracle Server 8-3 Log Force at Commit 8-4 Logical Ordering of Redo 8-5 Redo Log 8-6 Redo Log Buffer 8-7 Redo Generation 8-8 Writes to Redo Log Files 8-9 LGWR Algorithm 8-10 Redo Wait Events 8-12 Redo Latches 8-13 Optimizing the Redo Buffer 8-14 Tuning Redo Latch Contention 8-16 Redo-less Operations 8-17 Redo with NOLOGGING 8-18 Archiving 8-19 Events that Post the Archiver 8-20 vii

8 ARCH Process Flow 8-21 Archiver Operations 8-22 Tuning ARCH 8-23 Summary 8-26 viii

Oracle Database 10g: New Manageability Features

Oracle Database 10g: New Manageability Features Student Guide D17030GC10 Edition 1.0 September 2003 D38639 Author Lex de Haan Technical Contributors and Reviewers Jean-Francois Verrier Christine Jeal Martin