Oracle Database 11g: SQL Tuning Workshop. Student Guide

Transcription

1 Oracle Database 11g: SQL Tuning Workshop Student Guide D52163GC10 Edition 1.0 June 2008

2 Author Jean-François Verrier Technical Contributors and Reviewers Muriel Fry (Special thanks) Joel Goodman Harald van Breederode Jörn Bartels Pekka Siltala Bernard Soleillant James Spiller Clay Fuller Ira Singer Christopher Andrews Magnus Isaksson Sean Kim Trevor Bauwen Yash Jain Copyright 2008, Oracle. All rights reserved. Disclaimer This document contains proprietary information and is protected by copyright and other intellectual property laws. You may copy and print this document solely for your own use in an Oracle training course. The document may not be modified or altered in any way. Except where your use constitutes "fair use" under copyright law, you may not use, share, download, upload, copy, print, display, perform, reproduce, publish, license, post, transmit, or distribute this document in whole or in part without the express authorization of Oracle. The information contained in this document is subject to change without notice. If you find any problems in the document, please report them in writing to: Oracle University, 500 Oracle Parkway, Redwood Shores, California USA. This document is not warranted to be error-free. Restricted Rights Notice If this documentation is delivered to the United States Government or anyone using the documentation on behalf of the United States Government, the following notice is applicable: U.S. GOVERNMENT RIGHTS The U.S. Government s rights to use, modify, reproduce, release, perform, display, or disclose these training materials are restricted by the terms of the applicable Oracle license agreement and/or the applicable U.S. Government contract. Trademark Notice Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Editors Amitha Narayan Raj Kumar Graphic Designer Priya Saxena Publishers Jothi Lakshmi Veena Narasimhan

3 Contents 1 Exploring the Oracle Database Architecture Objectives 1-2 Oracle Database Server Architecture: Overview 1-3 Connecting to the Database Instance 1-4 Oracle Database Memory Structures: Overview 1-6 Database Buffer Cache 1-7 Redo Log Buffer 1-8 Shared Pool 1-9 Processing a DML Statement: Example 1-10 COMMIT Processing: Example 1-11 Large Pool 1-12 Java Pool and Streams Pool 1-13 Program Global Area (PGA) 1-14 Background Process Roles 1-15 Automatic Shared Memory Management 1-16 Automated SQL Execution Memory Management 1-17 Automatic Memory Management 1-18 Database Storage Architecture 1-19 Logical and Physical Database Structures 1-21 Segments, Extents, and Blocks 1-23 SYSTEM and SYSAUX Tablespaces 1-24 Summary 1-25 Practice 1: Overview Introduction to SQL Tuning Objectives 2-2 Reasons for Inefficient SQL Performance 2-3 Inefficient SQL: Examples 2-4 Performance Monitoring Solutions 2-6 Monitoring and Tuning Tools: Overview 2-8 EM Performance Pages for Reactive Tuning 2-9 Tuning Tools: Overview 2-10 SQL Tuning Tasks: Overview 2-11 CPU and Wait Time Tuning Dimensions 2-12 Scalability with Application Design, Implementation, and Configuration 2-13 iii

4 Common Mistakes on Customer Systems 2-14 Proactive Tuning Methodology 2-16 Simplicity in Application Design 2-17 Data Modeling 2-18 Table Design 2-19 Index Design 2-20 Using Views 2-21 SQL Execution Efficiency 2-22 Writing SQL to Share Cursors 2-24 Performance Checklist 2-25 Summary 2-26 Practice 2: Overview Introduction to the Optimizer Objectives 3-2 Structured Query Language 3-3 SQL Statement Representation 3-4 SQL Statement Implementation 3-5 SQL Statement Processing: Overview 3-6 SQL Statement Processing: Steps 3-7 Step 1: Create a Cursor 3-8 Step 2: Parse the Statement 3-9 Steps 3 and 4: Describe and Define 3-10 Steps 5 and 6: Bind and Parallelize 3-11 Steps 7 Through SQL Statement Processing PL/SQL: Example 3-13 SQL Statement Parsing: Overview 3-14 Why Do You Need an Optimizer? 3-16 Optimization During Hard Parse Operation 3-18 Transformer: OR Expansion Example 3-19 Transformer: Subquery Unnesting Example 3-20 Transformer: View Merging Example 3-21 Transformer: Predicate Pushing Example 3-22 Transformer: Transitivity Example 3-23 Cost-Based Optimizer 3-24 Estimator: Selectivity 3-25 Estimator: Cardinality 3-26 Estimator: Cost 3-27 Plan Generator 3-28 Controlling the Behavior of the Optimizer 3-29 Optimizer Features and Oracle Database Releases 3-34 iv

5 Summary 3-35 Practice 3: Overview Optimizer Operators Objectives 4-2 Row Source Operations 4-3 Main Structures and Access Paths 4-4 Full Table Scan 4-5 Full Table Scans: Use Cases 4-6 ROWID Scan 4-7 Sample Table Scans 4-8 Indexes: Overview 4-10 Normal B*-tree Indexes 4-12 Index Scans 4-13 Index Unique Scan 4-14 Index Range Scan 4-15 Index Range Scan: Descending 4-16 Descending Index Range Scan 4-17 Index Range Scan: Function-Based 4-18 Index Full Scan 4-19 Index Fast Full Scan 4-20 Index Skip Scan 4-21 Index Skip Scan: Example 4-23 Index Join Scan 4-24 The AND-EQUAL Operation 4-25 B*-tree Indexes and Nulls 4-26 Using Indexes: Considering Nullable Columns 4-27 Index-Organized Tables 4-28 Index-Organized Table Scans 4-29 Bitmap Indexes 4-30 Bitmap Index Access: Examples 4-31 Combining Bitmap Indexes: Examples 4-32 Combining Bitmap Index Access Paths 4-33 Bitmap Operations 4-34 Bitmap Join Index 4-35 Composite Indexes 4-36 Invisible Index: Overview 4-37 Invisible Indexes: Examples 4-38 Guidelines for Managing Indexes 4-39 Investigating Index Usage 4-41 Practice 4: Overview 4-43 v

6 Clusters 4-44 When Are Clusters Useful? 4-45 Cluster Access Path: Examples 4-47 Sorting Operators 4-48 Buffer Sort Operator 4-49 Inlist Iterator 4-50 View Operator 4-51 Count Stop Key Operator 4-52 Min/Max and First Row Operators 4-53 Join Methods 4-54 Nested Loops Join 4-55 Nested Loops Join: Prefetching 4-56 Nested Loops Join: 11g Implementation 4-57 Sort Merge Join 4-58 Hash Join 4-59 Cartesian Join 4-60 Join Types 4-61 Equijoins and Nonequijoins 4-62 Outer Joins 4-63 Semijoins 4-64 Antijoins 4-65 Other N-Array Operations 4-66 Filter Operations 4-67 Concatenation Operation 4-68 UNION [ALL], INTERSECT, MINUS 4-69 Result Cache Operator 4-70 Summary 4-71 Practice 4: Overview Interpreting Execution Plans Objectives 5-2 What Is an Execution Plan? 5-3 Where to Find Execution Plans? 5-4 Viewing Execution Plans 5-6 The EXPLAIN PLAN Command 5-7 The EXPLAIN PLAN Command: Example 5-9 PLAN_TABLE 5-10 Displaying from PLAN_TABLE: Typical 5-11 Displaying from PLAN_TABLE: ALL 5-12 Displaying from PLAN_TABLE: ADVANCED 5-14 vi

7 AUTOTRACE 5-15 The AUTOTRACE Syntax 5-16 AUTOTRACE: Examples 5-17 AUTOTRACE: Statistics 5-18 Using the V$SQL_PLAN View 5-20 The V$SQL_PLAN Columns 5-21 The V$SQL_PLAN_STATISTICS View 5-22 Links Between Important Dynamic Performance Views 5-23 Querying V$SQL_PLAN 5-25 Automatic Workload Repository (AWR) 5-27 Managing AWR with PL/SQL 5-29 Important AWR Views 5-31 Querying the AWR 5-32 Generating SQL Reports from AWR Data 5-34 SQL Monitoring: Overview 5-35 SQL Monitoring Report: Example 5-37 Interpreting an Execution Plan 5-40 Execution Plan Interpretation: Example Execution Plan Interpretation: Example Execution Plan Interpretation: Example Reading More Complex Execution Plans 5-48 Reviewing the Execution Plan 5-49 Looking Beyond Execution Plans 5-50 Summary 5-51 Practice 5: Overview Case Study: Star Transformation Objectives 6-2 The Star Schema Model 6-3 The Snowflake Schema Model 6-4 Star Query: Example 6-5 Execution Plan Without Star Transformation 6-6 Star Transformation 6-7 Star Transformation: Considerations 6-8 Star Transformation: Rewrite Example 6-9 Retrieving Fact Rows from One Dimension 6-10 Retrieving Fact Rows from All Dimensions 6-11 Joining the Intermediate Result Set with Dimensions 6-12 Star Transformation Plan: Example Star Transformation: Further Optimization 6-14 vii

8 Using Bitmap Join Indexes 6-15 Star Transformation Plan: Example Star Transformation Hints 6-17 Bitmap Join Indexes: Join Model Bitmap Join Indexes: Join Model Bitmap Join Indexes: Join Model Bitmap Join Indexes: Join Model Summary 6-22 Practice 6: Overview Optimizer Statistics Objectives 7-2 Optimizer Statistics 7-3 Types of Optimizer Statistics 7-4 Table Statistics (DBA_TAB_STATISTICS) 7-5 Index Statistics (DBA_IND_STATISTICS) 7-6 Index Clustering Factor 7-8 Column Statistics (DBA_TAB_COL_STATISTICS) 7-10 Histograms 7-11 Frequency Histograms 7-12 Viewing Frequency Histograms 7-13 Height-Balanced Histograms 7-14 Viewing Height-Balanced Histograms 7-15 Histogram Considerations 7-16 Multicolumn Statistics: Overview 7-17 Expression Statistics: Overview 7-19 Gathering System Statistics 7-20 Gathering System Statistics: Example 7-22 Mechanisms for Gathering Statistics 7-24 Statistic Preferences: Overview 7-25 When to Gather Statistics Manually 7-27 Manual Statistics Gathering 7-28 Manual Statistics Collection: Factors 7-29 Managing Statistics Collection: Example 7-30 Optimizer Dynamic Sampling: Overview 7-31 Optimizer Dynamic Sampling at Work 7-32 OPTIMIZER_DYNAMIC_SAMPLING 7-33 Locking Statistics 7-34 Summary 7-35 Practice 7: Overview 7-36 viii

9 8 Using Bind Variables Objectives 8-2 Cursor Sharing and Different Literal Values 8-3 Cursor Sharing and Bind Variables 8-4 Bind Variables in SQL*Plus 8-5 Bind Variables in Enterprise Manager 8-6 Bind Variable Peeking 8-7 Cursor Sharing Enhancements 8-9 The CURSOR_SHARING Parameter 8-11 Forcing Cursor Sharing: Example 8-12 Adaptive Cursor Sharing: Overview 8-13 Adaptive Cursor Sharing: Architecture 8-14 Adaptive Cursor Sharing: Views 8-16 Adaptive Cursor Sharing: Example 8-18 Interacting with Adaptive Cursor Sharing 8-19 Summary 8-20 Practice 8: Overview Using Optimizer Hints Objectives 9-2 Optimizer Hints: Overview 9-3 Types of Hints 9-4 Specifying Hints 9-5 Rules for Hints 9-6 Hint Recommendations 9-7 Optimizer Hint Syntax: Example 9-8 Hint Categories 9-9 Optimization Goals and Approaches 9-10 Hints for Access Paths 9-11 The INDEX_COMBINE Hint: Example 9-15 Hints for Query Transformation 9-17 Hints for Join Orders 9-20 Hints for Join Operations 9-21 Additional Hints 9-23 Hints and Views 9-26 Global Table Hints 9-28 Specifying a Query Block in a Hint 9-29 Specifying a Full Set of Hints 9-30 Summary 9-31 Practice 9: Overview 9-32 ix

10 10 Application Tracing Objectives 10-2 End-to-End Application Tracing Challenge 10-3 End-to-End Application Tracing 10-4 Location for Diagnostic Traces 10-5 What Is a Service? 10-6 Use Services with Client Applications 10-7 Tracing Services 10-8 Use Enterprise Manager to Trace Services Service Tracing: Example Session Level Tracing: Example Trace Your Own Session The trcsess Utility Invoking the trcsess Utility The trcsess Utility: Example SQL Trace File Contents SQL Trace File Contents: Example Formatting SQL Trace Files: Overview Invoking the tkprof Utility tkprof Sorting Options Output of the tkprof Command tkprof Output with No Index: Example tkprof Output with Index: Example Summary Practice 10: Overview Automating SQL Tuning Objectives 11-2 Tuning SQL Statements Automatically 11-3 Application Tuning Challenges 11-4 SQL Tuning Advisor: Overview 11-5 Stale or Missing Object Statistics 11-6 SQL Statement Profiling 11-7 Plan Tuning Flow and SQL Profile Creation 11-8 SQL Tuning Loop 11-9 Access Path Analysis SQL Structure Analysis SQL Tuning Advisor: Usage Model Database Control and SQL Tuning Advisor Running SQL Tuning Advisor: Example x

11 Implementing Recommendations SQL Access Advisor: Overview SQL Access Advisor: Usage Model Possible Recommendations SQL Access Advisor Session: Initial Options SQL Access Advisor: Workload Source SQL Access Advisor: Recommendation Options SQL Access Advisor: Schedule and Review SQL Access Advisor: Results SQL Access Advisor: Results and Implementation SQL Tuning Loop Automatic SQL Tuning Automatic Tuning Process Automatic SQL Tuning Controls Automatic SQL Tuning Task Configuring Automatic SQL Tuning Automatic SQL Tuning: Result Summary Automatic SQL Tuning: Result Details Automatic SQL Tuning Result Details: Drilldown Automatic SQL Tuning Considerations Summary Practice 11: Overview Appendix A: Practices and Solutions Index xi