Donald K. Burleson Dave Ensor Christopher Foot Lisa Hernandez Mike Hordila Jonathan Lewis Dave Moore Arup Nanda John Weeg

Transcription

1 Oracle Space Management Handbook Donald K. Burleson Dave Ensor Christopher Foot Lisa Hernandez Mike Hordila Jonathan Lewis Dave Moore Arup Nanda John Weeg

2 Oracle Space Management Handbook By: Donald K. Burleson, Dave Ensor, Christopher Foot, Lisa Hernandez, Mike Hordila, Jonathan Lewis, Dave Moore, Arup Nanda, John Weeg Copyright 2003 by BMC Software and DBAzine. Used with permission. Printed in the United States of America. Series Editor: Donald K. Burleson Production Manager: John Lavender Production Editor: Teri Wade Cover Design: Bryan Hoff Printing History: August, 2003 for First Edition Oracle, Oracle7, Oracle8, Oracle8i and Oracle9i are trademarks of Oracle Corporation. Many of the designations used by computer vendors to distinguish their products are claimed as Trademarks. All names known to Rampant TechPress to be trademark names appear in this text as initial caps. The information provided by the authors of this work is believed to be accurate and reliable, but because of the possibility of human error by our authors and staff, BMC Software, DBAZine and Rampant TechPress cannot guarantee the accuracy or completeness of any information included in this work and is not responsible for any errors, omissions or inaccurate results obtained from the use of information or scripts in this work. Links to external sites are subject to change; dbazine.com, BMC Software and Rampant TechPress do not control or endorse the content of these external web sites, and are not responsible for their content. ISBN: iii

3 Table of Contents Conventions Used in this Book... xiv About the Authors... xvi Foreword...xix Section One - Datafiles Chapter 1 - Measuring Oracle Segment I/O... 1 What is Really Going On? by John Weeg...1 Theory...1 Test It...2 What Happens When We Update?...4 What Else?...5 So What?...5 Chapter 2 - Datafile Resizing Tips...6 Setting Free Your Space by John Weeg...6 Alter Database...7 Double Checking the Work...9 Chapter 3 - Reducing Disk I/O on Oracle Datafiles Oracle Expert Tuning Secrets to reduce disk I/O by Don Burleson Oracle tuning and Disk I/O Tuning with RAM Data Buffers The KEEP Pool Locating Tables and Indexes for the KEEP Pool The RECYCLE Pool Using Multiple Block Sizes Disk I/O Tuning STATSPACK Reports for Oracle Datafiles Conclusion Chapter 4 - Measuring Data Segment Statistics iv Oracle Space Management Handbook

4 Digging at the Segment Level : Performance Diagnosis Reaches A Deeper Level by Arup Nanda Background / Overview Setting the Statistics Levels Segment Level Statistics Collection Column Explanation Examining Detailed Statistics Improvements Case Study Solution Conclusion Chapter 5 - Optimizing Oracle Physical Design Optimal Physical Database Design for Oracle8i by Dave Ensor Introduction Physical Database Design What is Physical Database Design? Database Block Structure Block Size Unstructured Data Freelists Extents AutoExtension Partitioning Index Compression Index Organized Tables (IOT's) Insert Times Retrieval Times Application Impact Online Table Reorganization Temporary Tables Application Impact Locally Managed Tablespaces Table of Contents v

5 Transportable Tablespaces Conclusions Chapter 6 - Verifying Segment Backup Scripts Did the Backup Work? by John Weeg Problem How Do We Know? Parsing This String Bring It In Use It Use it Elsewhere Chapter 7 - Data Segment Update Internals How Much Does an Update Cost? by Jonathan Lewis A Brief History of Screen Generators What Does It Cost to Update a Column? But There's More Triggers Indexes Referential Integrity There's Always a Trade-off Conclusion Chapter 8 - Segment Transaction Slot Internals Interested Transaction List (ITL) Waits Demystified by Arup Nanda What is ITL? What Is an ITL Wait Simulation How to Reduce ITL Waits How to Diagnose the ITL Wait What INITRANS Value is Optimal Automatic Block Management in Oracle9i Conclusion Section Two - Tablespaces vi Oracle Space Management Handbook

6 Chapter 9 - Automated Space Cleanup in Oracle Automated Space Cleanup in Oracle by Mike Hordila Stray Temporary Segments Manual Cleanup of Temporary Segments Recommendations Regarding Temporary Segments Locking Problems with Rollback Segments Recommendations Regarding Rollback Segments Automated Space Cleanup Prerequisites Overview of the Package Setup Chapter 10 - Using Oracle TEMP Files Temporarily Yours: Tempfiles by John Weeg Don't Wait to Create Don't Backup Don't Recover Don't Copy for Standby Don't Add Overhead Give It a Try Chapter 11 - Monitoring TEMP Space Usage Who Took All the TEMP? by John Weeg Where Are My TEMP Tablespaces? Show Me the Objects Who Are the Users? A Happy Ending Chapter 12 - Oracle9i Self-Management Features Oracle9i Self-Management Features: The Early Winners by Dave Ensor Introduction Test Environment Self-Management Table of Contents vii

7 Goals Examples Instance Parameter Management Self-Tuning Memory Management Memory Made Simple PGA Aggregate Target Cache Advice Automatic Undo Management Background Rollback Segments The Oracle9i Solution Database Resource Manager Unused Index Identification Oracle Managed Files Conclusions Chapter 13 - Internals of Locally-Managed Tablespaces Locally Managed Tablespaces by Jonathan Lewis Tablespaces Past and Present The Past The Present Where Are the Benefits? Conclusion Chapter 14 - Multiple Block Sizes in Oracle9i Using Multiple Block Sizes in Oracle9i by Don Burleson Indexes and Large Data Blocks Allocating Objects into Multiple Block Buffers Tools for Viewing Data Buffer Usage Creating Separate Data Buffers Conclusion Section Three - Tables Chapter 15 - Automated Table Reorganization in Oracle8i150 viii Oracle Space Management Handbook

8 Automated Table/Index Reorganization In Oracle8i by Mike Hordila When Reorganizing, How Many Extents to Use? Possible Reorganizing Strategies Assumptions and Experimental Figures Some Procedures Related to Table Reorganization Important Issues Regarding Table/Index Moving/Rebuilding The Behavior of the "Alter Table/Index Move/Rebuild" Commands Limitations of the "ALTER TABLE MOVE" Command: Manual Object Reorganization Step Step Automated Object Reorganization Prerequisites Associated Tables Overview of the Package Setup Chapter 16 - Using External Table in Oracle9i External Tables in Oracle9i by Dave Moore Example Limitations Performance Practical Applications Database Administration Chapter 17 - Instructors Guide to External Tables An Oracle Instructor's Guide to Oracle9i - External Tables by Christopher Foot External Tables Tablespace Changes Online Table Reorganizations Index Monitoring Table of Contents ix

9 Section Four - Indexes Chapter 18 - Using Locally-Managed Indexes Locally Managed Indexes by John Weeg Rebuild in the same Tablespace No Fragment to the Rescue More Than One What Goes Where Break Points Script Conclusion Chapter 19 - Sizing Oracle Index Segments Part How Big Should This Index Be? by John Weeg B-tree Theory Estimate Leafs Estimate Branches Making the Index Chapter 20 - Sizing Oracle Index Segments Part Is This Index the Right Size? by John Weeg Validate Structure Dba_Indexes Logical Steps for Resizing and Defragging All Together Now Section Five - Partitioning Chapter 21 - Oracle Partitioning Design Partitioning in Oracle 9i, Release 2 by Lisa Hernandez Introduction Background Partitioning Defined When To Partition Different Methods of Partitioning x Oracle Space Management Handbook

10 Partitioning Of Tables Range Partitioning Hash Partitioning List Partitioning Composite Range-Hash Partitioning Composite Range-List Partitioning Conclusion Chapter 22 - Oracle Partitioning Design Part Partitioning in Oracle 9i, Release 2 -- Part 2 by Lisa Hernandez Introduction Background Globally Partitioned Indexes Locally Partitioned Indexes When to Use Which Partitioning Method Real Life Example Conclusion Chapter 23 - Effective Segment Partitioning Part Perils and Pitfalls in Partitioning Part 1 by Arup Nanda Plan Table Revisited The New Tool DBMS_XPLAN Partition Pruning or Elimination Partition-wise Joins Character Value in Range Partitioning Chapter 24 - Effective Segment Partitioning Part Perils and Pitfalls in Partitioning Part 2 by Arup Nanda Multi-Column Partition Keys Subpartition Statistics PARTNAME GRANULARITY Rule Based Optimizer Coalesce vs. Merge Table of Contents xi

11 Other Questions What about Rebuild Partition and Global Indexes? While using partitioning, should you use bind variables? How many partitions can be defined on a table? Section Six - Replication Chapter 25 - Multi-Master Replication A Four-phase Approach to Procedural Multi-master Replication by Don Burleson Introduction Why Consider Oracle Multi-master Replication? Oracle Multi-master Replication Multi-master Conflicts and Resolutions Conflict Types Conflict Resolution Mechanisms Implementing Procedural Multi-master Replication Phase I: Pre-configuration Steps for Multi-master Replication Phase II: Set-up REPADMIN User and Database Links Phase III: Create the Master Database and Refresh Groups Phase IV: Monitoring Multi-master Replication Resources for Defining Multi-master Replication Conclusion References Chapter 26 - Replication Management Automated Replication Management by Mike Hordila Basic Replication Automated Replication Management Prerequisites Associated Tables Overview of the Package Setup Test Environment Chapter 27 - Replication Master Table xii Oracle Space Management Handbook

12 Altering the Master Table in a Snapshot Replication Environment without Recreating the Snapshot by Arup Nanda Background The Usual Method The Alternative Approach Detailed Steps Conclusion Index Table of Contents xiii

13 Measuring Oracle Segment I/O What is Really Going On? CHAPTER 1 We are taught, from the beginning, that we want to separate our tablespaces onto different mount points or drives to minimize I/O level contention. There are devices that minimize this physical level contention; but most of my smaller clients don't have these devices, so we still have this concern. How do we see what is really at the file level? Given a smaller system, where I can fit the majority of the database into memory; does the I/O matter? Theory Ideally all the data we want to work with are in memory and no I/O is needed. In reality, you usually can't count on this being the case. So, our goal is to try to minimize the disk physical movement for any given data request. For example, if the index and the data are on the same disk, there is movement needed for the index and then the same disk must move for the data. If the next read wants the next record, then we must move back for the index and back again for the data. We have made the read for the data and the read for the index get in each other's way. The theory says that all objects that might be used in the same transaction should be on different mount points. So we have the following minimum mount points: What is Really Going On? 1

14 System tablespace Data tablespace Index tablespace Rollback segments Archive logs Temporary tablespace These six mount points would give us our basic good system setup. Let's put this theory to the test. Test It There are two very useful dynamic system views, v$datafile and v$tempfile, that will allow us to test this theory. Previous to 8.1 you won't find v$tempfile. These both have the same layout, so I will just work with v$datafile for the testing. The fields we are interested in first are the number of physical reads/writes and the number of blocks read and written. This view gives the statistics since instance startup so we have created a table to isolate and compare the results of v$datafile for the current activity: create table phy_io tablespace data01 storage (initial 64k next 64k pctincrease 0) pctfree 0 pctused 80 unrecoverable as select file#,phyrds,phywrts,phyblkrd,phyblkwrt from v$filestat; So let's see what we have right now in a newly started instance - the only activity has been to create this table: 2 Oracle Space Management Handbook