Database Performance on AIX in DB2 UDB and Oracle Environments

Transcription

1 Database Performance on AIX in DB2 UDB and Oracle Environments Nigel Griffiths, James Chandler, João Marcos Costa de Souza, Gerhard Müller, Diana Gfroerer International Technical Support Organization SG

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3 International Technical Support Organization SG Database Performance on AIX in DB2 UDB and Oracle Environments December 1999

4 Take Note! Before using this information and the product it supports, be sure to read the general information in Appendix E, Special notices on page 411. First Edition (December 1999) This edition applies to Version 6.1 of DB2 Universal Database - Enterprise Edition, referred to as DB2 UDB; Version 7 of Oracle Enterprise Edition and Release of Oracle8i Enterprise Edition, referred to as Oracle; for use with AIX Version Comments may be addressed to: IBM Corporation, International Technical Support Organization Dept. JN9B Building 003 Internal Zip Burnet Road Austin, Texas When you send information to IBM, you grant IBM a non-exclusive right to use or distribute the information in any way it believes appropriate without incurring any obligation to you. Copyright International Business Machines Corporation All rights reserved. Note to U.S Government Users Documentation related to restricted rights Use, duplication or disclosure is subject to restrictions set forth in GSA ADP Schedule Contract with IBM Corp.

5 Contents Preface....xv How this book is organized...xv The team that wrote this redbook....xvi Commentswelcome...xix Chapter 1. Introduction to this redbook...1 Part 1. RDBMS concepts...3 Chapter 2. Introduction into relational database system concepts WhatisanRDBMS? What does an RDBMS provide? The database performance trick What are the components of an RDBMS? Defining the RDBMS terms and ideas RDBMSterms Structured Query Language Howdowemakethedatasafe? Backupandperformance Backupmedia Fullorpartialbackup Physicalandlogicalbackup Onlineandoff-linebackup Backup recommendations Chapter 3. Types of workload OnlineTransactionProcessing(OLTP) OnlineAnalyticalProcessing(OLAP) Decision Support Systems (DSS) Data warehouse Datamart Business Intelligence (BI) Datamining Enterprise Resource Planning (ERP) e-business Reporting Chapter 4. Specific databases DB2 UDB Database architecture Memorystructures Logical storage structures Copyright IBM Corp iii

6 4.1.3 Physicalstoragestructures Processes SQL extensions - Stored procedures Administrationtools Oracle database architecture Memorystructures Logical storage structures Physicalstoragestructures Processes SQL extensions - Stored procedures Administrationtools...77 Chapter 5. Parallel databases Parallelconceptsindatabaseenvironments Sharedmemory Shareddisks Sharednothing DB2 UDB Enterprise - Extended Edition (EEE) Conceptsandfunctionality Optimizer Inter-partitionandintra-partitionparallelism Hardwareimplementation OracleParallelserver ParallelOraclearchitecture VirtualSharedDisk(VSD) Distributed Lock Manager (DLM) Advantages and disadvantages of parallel databases Part 2. System design and sizing for optimal performance...99 Chapter 6. Sizing a database system Sizingconstraints Sizing techniques Sizingfromthedatasize Sizingfromtransactionrates Sizingfromusernumbers Sizingforaparticularapplication CPU goals and sizing Uniprocessor(UP)Systems SymmetricMultiprocessor(SMP)Systems CPU utilization Memory goals and sizing AIX operating system iv Database Performance on AIX in DB2 UDB and Oracle Environments

7 6.5.2 AIXfilesystemcache(AIXbuffercache) RDBMScacheandstructures User applications and database connections Disk goals and sizing General database sizing - High-level Specifictablebytablesizing-Detailedlevel Which disk size to choose Diskprotection Balancing a system via the component costs Chapter 7. Designing a system for an RDBMS Workingspace BasicandfutureAIXresources Basicandfutureapplicationresources BasicRDBMSresources FutureRDBMSresources Workloadconsiderations Networkconsiderations Memoryanddatabaseconsiderations DB2 UDB memory requirements Oracle memory requirements System resource utilization Can the database be backed up and restored? DB2 UDB backup/restore scenario Oracle backup/restore scenario General backup considerations Copingwithgrowth DB2 UDB reorganization method Oracle reorganization method When and how to avoid database reorganization Coping with large, unexpected growth Expectedgrowthareas Loading large amounts of data Performance versus availability Production, development, and testing on the same machine Production Development Testing Hybridmachines AIX and RDBMS upgrades Chapter 8. Designing a disk subsystem Disk subsystem design approach v

8 8.2 Bandwidth related performance considerations Physical database layout considerations Database datafile distribution Logical Volume Manager (LVM) Concepts PhysicalPartitionstripingversusLVMfinestriping UseofLVMpolicies RawlogicalvolumesversusJournaledFileSystems(JFS) RAIDLevelsoverviewandperformanceconsiderations RAIDLevel RAIDLevel RAIDLevel2andLevel RAIDLevel RAIDLevel RAID ComparisonofRAIDLevels RAID5versusAIXLVMmirroring UseofMirrorWriteConsistency(MWC) SerialStorageArchitecture(SSA) Technology overview SSAspecificperformanceconsiderations Integrateddiskstoragesystems IBMEnterpriseStorageServer(ESS) Diskperformancemeasurementsandobservations Choosing your disk subsystem Part 3. System optimization Chapter 9. Implementing your database Hardware and AIX ready check list Pre-startingchecklist Database data Hardwaretesting InstallingtheRDBMScode Physical layout of the database Scriptingthebuild Buildasmallcutdownsystem Afterinstallation Backupandrecoverytest Chapter 10. Monitoring an RDBMS system for performance RDBMStools DB2UDBmonitoringtools Oraclemonitoringtools vi Database Performance on AIX in DB2 UDB and Oracle Environments

9 10.2 Regular monitoring, ad-hoc, or alert method usage Regular monitoring method Ad-hocmonitoringmethod Alertmonitoringmethod Performancemonitoringscripts Monitoring and tuning responsibilities When should a performance problem be reported and to whom? Whatareyoulookingfor? Chapter 11. Tuning an RDBMS system Tuning skills Reference manuals and books About RDBMS tuning and RDBMS performance tuning books Tuningstrategy Formalfinetuningmethod Cleardefinitionofthesuccesscriteria Limitingtheactivity Iteration One change at a time Decidingpriorities Hotspots Wellknownimportantareas Reproducible workloads How to measure response time Carefulinstrumentationandmeasurement Documentation Scheduling the tests Verifyingtheimprovement Thetuningteam Change all at once method Ignore the rumors Gatheringtheinformation Checkforerrors Upgradetothelatestfixlevels Investigatingthesystem Checkandsettopperformanceparameters Bottlenecks, utilization, and resources Utilization goals InsufficientCPUandlatentdemand Insufficientmemory InsufficientdiskI/O Insufficientnetworkresources Insufficientlogicalresourceaccess vii

10 11.7 What can we tune? Tuning window Classicmistakelist Chapter 12. DB2 UDB tuning Performanceimprovementprocess General tuning elements Operational performance considerations Environmentalconsiderations Applicationconsiderations Systemcatalogstatistics SQLcompiler SQLExplainfacility UsingtheDB2UDBgovernor Scalingtheconfiguration MemoryusagebyDB2UDB What can you change to make a difference? Whataretheoptions? Database manager configuration parameters Database parameters DB2UDBregistryvariables Whichoptionswillmakealargedifference? Buffer pool size (buffpage) NumberofI/Oservers(num_ioservers) Number of asynchronous page cleaners (num_iocleaners) Changed pages threshold (chngpgs_thresh) Sort heap size (sortheap) Sort heap threshold (sheapthres) Statement heap size (stmtheap) Packagecachesize(pckcachesz) Database heap size (dbheap) Catalog cache size (catalogcache_sz) Log buffer size (logbufsz) Maximum number of agents (maxagents) Maximumstorageforlocklist(locklist) Maximum percent of lock list before escalation (maxlocks) Maximum query degree of parallelism (max_querydegree) DB2MEMDISCLAIMandDB2MEMMAXFREE DB2_PARALLEL_IO DB2_STRIPED_CONTAINERS Reorganizing tables Simulating through SYSSTAT views viii Database Performance on AIX in DB2 UDB and Oracle Environments

11 Chapter 13. Oracle tuning What can you change to make a difference? Oracletuningorder CheckthemostcommonAIXconfigurationmistakes Change control Failure to use asynchronous I/O Poordisksubsysteminstallation Redologdisks Paging space and monitoring paging Not allocating enough memory to Oracle PooruseofAIXdiskfeatures Busydisks CheckthemostcommonOraclemistakes Indexes Analysis BasicOracleparameters Analyze database tables and indexes Tuning hint categories for AIX and Oracle used in this chapter Evaluatethetop10Oracleparameters db_block_size db_block_buffers use_async_io or disk_asynch_io db_writers, db_writer_processes and dbwr_io_slaves shared_pool_size sort_area_size sql_trace timed_statistics optimizer_mode log_buffer rollback_segments OtherkeyOracleparameters Iterativefinetuningsteps Accessmethodtuning Memorytuning DiskI/Otuning CPUtuning Contentiontuning TuningAIXforOraclehints AIX asynchronous I/O AIX Logical Volume Manager or Oracle files Create logical volumes at a standardized size AIXJFSorrawdevices AIX disk geometry considerations ix

12 Namingconvention AIX sequential read ahead AIX paging space AIX paging rate Hotdiskremoval Disk sets for hot disk avoidance SMP balanced CPU utilization AdvancedAIXtuninghints AIX readv() feature AIXdirectI/O AIX write behind AIXdiskI/Opacing AIXprocessorbindingonSMP AIX spin count on SMP AIXprocesspriority AIXprocesstimeslice AIXfreememory AIXbuffercachesize Oracletuninghints Oracle installed according to Oracle Flexible Architecture Oracle ARCHIVEMODE Oraclecontrolfiles Oraclepost-waitkernelextensionforAIX Oracleblocksize OracleSGAsize Oracle database writers Oraclebuffercachehitratiotuning Split the database disks from the AIX disks Oracle redo log should have a dedicated disk Mirror the redo log or use RAID 5 fast-write cache option Oracle redo log groups or AIX mirrors Oracleparallelrecovery Oracle db_file_multiblock_read_count parameter Oracleredobufferlatch Oracleredobuffersize Oracle shared pool size Oracletablespaceandtablecreation NumberofOraclerollbacksegments Oracleparallelization Oraclearchiverbuffers OracleuseTRUNCATEratherthanDELETEallrows Oraclemarkingandbatchdeletingrows Oracle SQL*Loader I/O buffers x Database Performance on AIX in DB2 UDB and Oracle Environments

13 13.12 Othertuninghints NetworkTCP/IP Compiling programs with embedded Oracle SQL Books for Oracle database administration and tuning Chapter 14. Austin - we have a problem! Perfpmr-theperformancedatacollectiontool Getthelatestversionofperfpmr AIXmediasuppliedversion Beforeyouhaveaproblem Raising a Problem Management Record (PMR) PMRinformation Most common sources of database performance PMRs Avoidingthenextperformancecrisis Appendix A. AIX performance tools summary A.1 Summaryofperformancebottlenecks A.2 filemon-filei/omonitor A.3 iostat-diski/ostatistics A.4 lsattr-listattributes A.5 lscfg-listconfiguration A.6 lsdev-listdevices A.7 lslpp-listlicensedprogramproduce A.8 lslv-listlogicalvolume A.9 lsps-listpagingspace A.10 lspv-listphysicalvolume A.11 lsvg-listvolumegroup A.12 ncheck-inodecheck A.13 netpmon-networkmonitor A.14 nfsstat-networkfilesystemstatistics A.15 nmon-onlinemonitor A.16 no-networkoptions A.17 ps-processstate A.18 rmss - Reduced Memory System Simulator A.19 sar-systemactivityreporter A.20 schedtune-processschedulingtuning A.21 svmon-systemvirtualmemorymonitor A.22 vmstat - Virtual Memory Management Statistics A.23 vmtune-virtualmemorytuning Appendix B. Vital SQL B.1 DB2UDB B.1.1 List the existing tables on a database B.1.2 Describethestructureofthecolumnsinatable xi

14 B.1.3 Describe the indexes defined in a table and their structure B.1.4 Describe structure of the columns within a SELECT statement B.1.5 List all the tablespaces of a database B.1.6 List tablespace name, Id number, size, and space consumption B.1.7 Listthetablespacecontainers B.1.8 Enable all monitor switches B.1.9 Disableallmonitorswitches B.1.10 Checkthemonitorstatus B.1.11 Resetthemonitorcountersforaspecificdatabase B.1.12 Showthelocksexistingonadatabase B.1.13 List application number, status, idle time, and AIX processes B.1.14 List connected and effectively executing users B.1.15 Display the amount of memory being used for sort operations B.1.16 Display the number of deadlocks and lock escalations B.1.17 Display the number of attempted SQL COMMIT statements B.2 Oracle B.2.1 Oraclenumberoftransactions B.2.2 Buffer cache hit ratio - manual B.2.3 Buffercachehitratio-automatic B.2.4 Shared pool free memory B.2.5 Redologbuffertoosmall B.2.6 Rollbacksegment B.2.7 Oraclenestedexplainplan B.2.8 Oraclereportontablespaces B.2.9 Oraclereportontables B.2.10 Oraclereportonindexes B.2.11 Oracle report on database files B.2.12 Oraclereportonextents B.2.13 Oraclereportonparameters B.2.14 Oraclereportonfreespace Appendix C. Reference sheets C.1 SQL reference sheet C.1.1 Data Definition Language (DDL) commands C.1.2 Data Manipulation Language (DML) commands C.1.3 Operators C.1.4 SQLfunctions C.2 OracleSQLplusextensionsreferencesheet C.2.1 Running files and editing C.2.2 Lineeditingcommands C.2.3 Report/formatting commands C.2.4 Miscellaneous C.2.5 Help and additional settings xii Database Performance on AIX in DB2 UDB and Oracle Environments

15 C.3 OracleDBAreferencesheet C.3.1 Storage-Clause C.3.2 ALTER DATABASE C.3.3 ALTERINDEX C.3.4 ALTERROLLBACKSEGMENT C.3.5 ALTER SESSION C.3.6 ALTER SYSTEM C.3.7 ALTERTABLE C.3.8 ALTER TABLESPACE ALTERUSER C.3.9 ANALYZE C.3.10 CREATE DATABASE C.3.11 CREATEINDEX C.3.12 CREATEROLLBACKSEGMENT C.3.13 CREATETABLE C.3.14 CREATE TABLESPACE C.3.15 CREATEUSER C.3.16 CREATEVIEW C.3.17 DROP C.3.18 EXPLAINPLAN C.3.19 RENAME C.3.20 TRUNCATE C.3.21 UsefulOracleinternaltables C.4 DB2UDBDBAreferencesheet C.4.1 ALTERBUFFERPOOL C.4.2 ALTERTABLE C.4.3 ALTER TABLESPACE C.4.4 CREATE DATABASE C.4.5 CREATEINDEX C.4.6 CREATETABLE C.4.7 CREATETABLESPACE C.4.8 CREATEVIEW C.4.9 DROP C.4.10 EXPLAINPLAN C.4.11 RENAMETABLE C.4.12 UsefulDB2UDBinternalcatalogviews Appendix D. The Model Database used for testing in this redbook.401 D.1 Schema D.2 The model database tables D.3 The model database indexes D.4 OLTPworkloadgeneration D.5 DSSworkloadgeneration xiii

16 D.5.1 Query D.5.2 Query D.5.3 Query D.5.4 Query D.6 Model Database physical layout Appendix E. Special notices Appendix F. Related publications F.1 IBM Redbooks publications F.2 IBM Redbooks collections F.3 Otherresources F.4 ReferencedWebsites How to get IBM Redbooks IBM Redbooks fax order form List of abbreviations Index IBM Redbooks evaluation xiv Database Performance on AIX in DB2 UDB and Oracle Environments

17 Preface This redbook is designed to help system designers, system administrators, and database administrators design, size, implement, maintain, monitor, and tune a Relational Database Management System (RDBMS) for optimal performance on AIX. Relational Database Management Systems are a significant factor in the profit line of a company. They represent an important investment and their performance is often vital to the success of the company. This redbook contains hints and tips from experts that work on RDBMS performance every day. It also provides introductions to general database layout concepts from a performance point of view, design and sizing guidelines, tuning recommendations, and performance and tuning information for DB2 UDB and Oracle databases. Howthisbookisorganized This redbook consists of three major parts, that are adopted to a database s life cycle. The first part, RDBMS concepts contains information for a basic comprehension of RDBMSs, which is fundamental for understanding a database s performance behavior in order to design, size, and tune an RDBMS. This first part may be helpful if you want to learn about databases, as a reference to refresh your knowledge, or to help you understand why certain concepts have an impact on the database s performance. Different workloads are described in this part as well as the different architectures of DB2 UDB and Oracle databases and their parallel editions. System designers and system and database administrators will find this part especially useful. The second part, System design and sizing for optimal performance, covers the time before the database is actually implemented and deals with preparing the system. This second part gives sizing techniques and provides a number of rules of thumb, from our experience, that can help you to size your database system. The design chapters deal with different circumstances that have to be taken into account when a database system is planed, such as growth or backup and restore needs. We dedicated one chapter to the disk subsystem design since this is the most sensitive and essential area for good database performance. This second part is vital for system designers and architects. The third part, System optimization, covers the time from the database implementation on. First, we give hints and tips on how to optimize your Copyright IBM Corp xv

18 database implementation that go beyond the implementation documentation provided by database vendors. Then, we introduce some monitoring tools and methods that help you to keep track of your database s performance. The tuning chapters not only introduce different tuning methods and their benefits and drawbacks, they are, furthermore, filled with hints and tips and recommendations that help you tune the performance of your database system. There are AIX tuning hints and tips as well as separate chapters on DB2 UDB and Oracle tuning. The last chapter of this part should be used if all else fails. It provides hints and tips on how to open a problem record with IBM Software Service in a most effective way. The appendixes are provided for your reference. They contain reference sheets for database administrators, AIX performance tools, vital SQL, and we describe the Model Database that we used for our performance tests during the development of this redbook. The team that wrote this redbook This redbook was produced by a team of specialists from around the world working at the International Technical Support Organization, Austin Center. Diana Gfroerer is an International Technical Support Specialist for RS/6000 and AIX Performance at the International Technical Support Organization, Austin Center. She writes extensively and teaches IBM classes worldwide on all areas of AIX performance and tuning. Before joining the ITSO this year, Diana Gfroerer worked in AIX pre-sales Technical Support in Munich, Germany. She was leading the Region Central, EMEA, and World Wide Technical Skill Communities for AIX and PC Interoperability. Nigel Griffiths is a Performance Guru in the RS/6000 Pre-Sales Technical Support Group in the UK. He has 20 years experience with UNIX, seven of which are with IBM. His areas of expertise include C programming including UNIX kernel internals, performance tuning, and sizing of SMP and parallel Oracle databases. He has been a performance and database technical support leader for six years and has written extensively on performance and sizing. James Chandler is a Database Administrator with IBM Global Services in Lexington, Kentucky. He has four years of experience with storage management and database administration in distributed environments. He has worked at IBM for six years. His areas of expertise include implementing storage management solutions using ADSM and third party vendor tools, as well as database administration in SAP environments using Oracle and DB2. xvi Database Performance on AIX in DB2 UDB and Oracle Environments

19 Joao Marcos Costa de Souza is a DB2 UDB Support Professional in Sao Paulo, Brazil. He has seven years of experience in database administration and support in the field. He holds a degree in Computer Science and is an IBM Certified Solutions Expert - DB2 UDB V6.1 Database Administration and an Oracle Certified Professional Database Administrator. His areas of expertise include DB2 UDB EE and EEE implementation and support as well as performance and tuning. Gerhard Mueller is a Software Engineer with AIX Software Support in IBM Global Services in Mainz, Germany. He has five years of field experience in DB2 on AIX. He is a Certified Solutions Expert for DB2 UDB Administration. His areas of expertise include installation, administration, and problem determination in DB2 UDB EE and EEE environments. Thanks to the following people for their invaluable contributions to this project: Elizabeth Barnes International Technical Support Organization, Austin Center Richard Cutler International Technical Support Organization, Austin Center John Owczarzak International Technical Support Organization, Austin Center Temi Rose International Technical Support Organization, Austin Center Tetsuya Shirai International Technical Support Organization, Austin Center George Accapadi IBM Austin Mathew Accapadi IBM Austin John Aschoff IBM San Jose Stephen Atkins IBM UK Richard Bridgman IBM UK xvii

20 Doug Doole IBM Toronto Jessica Escott IBM Toronto Ian R. Finlay IBM Toronto Angel González IBM Germany Andreas Hoetzel IBM Austin Karl Huppler IBM Raleigh Joey V. James IBM Austin Dale Martin IBM San Francisco Dennis Massanari IBM Poughkeepsie Sean McKeough IBM Toronto Walter Orb IBM Foster City Ram Pandiri IBM Austin Dr. Norbert Pistoor IBM Germany Steve Pittman IBM San Francisco Lilian Romero IBM Austin xviii Database Performance on AIX in DB2 UDB and Oracle Environments

21 Berni Schiefer IBM Toronto Johnny Shieh IBM Austin Bill Topliss IBM Austin Aspi Wadia IBM Austin Eddine Walehiane IBM Austin David Whitworth IBM Austin Comments welcome Your comments are important to us! We want our Redbooks to be as helpful as possible. Please send us your comments about this or other Redbooks in one of the following ways: Fax the evaluation form found in IBM Redbooks evaluation on page 443 to the fax number shown on the form. Use the online evaluation form found at Send your comments in an Internet note to xix

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23 Chapter 1. Introduction to this redbook Relational Database Management Systems (RDBMS) become more and more the core IT systems of companies and large enterprises. They are vital for companies profit lines since RDBMS systems hold data, such as sales, stock, finances, and order income. This data has to be accessible by many people at the same time, often 24 hours a day, 7 days a week, especially since companies are extending their business onto a global market, and people need to have access to the systems from all time zones. Not only production data for the daily business, but also historical data is held in the companies database systems. This data is used for research and to provide information for major management decisions. High performance of these systems is very often vital for the success of a company. Customer orders have to be processed quickly, and available stock in the warehouses has to be found and assigned to the according order. Especially for companies with time-critical data, such as airlines, good performance is mandatory. Performance also becomes an increasing issue because the systems get bigger every year, the databases get more complex, and, last but not least, RDBMS systems mean a large investment in resources, both in money and people, and everybody wants value for their money. Database performance is a very wide area with many different aspects. It is dependent on a large number of factors, such as the hardware, the application, the workload, the layout of the disk subsystem, and an uncounted number of system and database parameters. Within this book, we want to share our knowledge and experience with you and help you to understand what database performance is all about and where to focus on when you plan, run, and tune a Relational Database Management System. We found that it was often hard to pin down clear facts since the alteration of one little parameter can change the whole picture, but we give you a number of rules of thumb, based on our experience, and we put a large amount of information down for you to make conclusions about the performance needs and impacts of your database system. We also hope to cut through many myths and legends about performance tuning options that are no longer true or that are only part of the truth as well as give you an update on the latest features of AIX that you can use to make your database perform at its best. Copyright IBM Corp

24 You might find this book to be helpful in any stage of your database s life cycle: In the planning and sizing stage, during implementation, and when running a productive database system. We adapted the structure of our redbook to this life cycle and subdivided it into three major parts: RDBMS concepts - Covering the concepts of Relational Database Management Systems, the different workload characteristics, and an introduction into both DB2 UDB and Oracle databases, including a brief introduction into parallel database systems. System design and sizing for optimal performance - Covering the pre-life phase of an RDBMS the sizing to meet the requirements of the predicted workload, and the system design and layout for optimal performance. System optimization - Focusing on the implementation of an RDBMS and the monitoring and tuning tasks once the database is installed. This book is written from an AIX and RS/6000 point of view and focuses on how an RDBMS can use the advanced features of these products. Even though we are covering DB2 UDB and Oracle databases in more detail, a large part of the book also applies to any other Relational Database Management System. We chose DB2 UDB and Oracle because they represent 80 percent of all databases installed on RS/6000s, and 65 percent of the RS/6000 Enterprise and SP Systems run a version of these popular databases. Database design or application programming are large subjects that are common to all platforms. There is a wide range of literature available on these subjects; therefore, we do not cover these subjects in this redbook, nor do we go into great detail on Structured Query Language (SQL). Please refer to Appendix F, Related publications on page 415 for some useful books. Appendix 3 has a simple quick reference sheet on SQL, useful if you are sitting in front of the machine trying to remember a particular SQL statement in order to get certain information from the database. Parallel databases are briefly mentioned so that you know when to consider them. However, covering parallel database design and performance exceeds the scope of this redbook. Designing, sizing, and tuning an RDBMS is rather an art than a science, and it requires a lot of technical skills and personal experience. This book, therefore, is a valuable source of information on your way of becoming a professional RDBMS performance expert. 2 Database Performance on AIX in DB2 UDB and Oracle Environments