IBM Informix. IBM Informix Dynamic Server Performance Guide. Version 11.1 G

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1 IBM Informix Version 11.1 IBM Informix Dynamic Server Performance Guide G

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3 IBM Informix Version 11.1 IBM Informix Dynamic Server Performance Guide G

4 Note: Before using this information and the product it supports, read the information in Notices on page C-1. This document contains proprietary information of IBM. It is provided under a license agreement and is protected by copyright law. The information contained in this publication does not include any product warranties, and any statements provided in this publication should not be interpreted as such. When you send information to IBM, you grant IBM a nonexclusive right to use or distribute the information in any way it believes appropriate without incurring any obligation to you. Copyright International Business Machines Corporation 1996, All rights reserved. US Government Users Restricted Rights Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp.

5 Contents Introduction xi In This Introduction xi About This Publication xi Topics Beyond the Scope of This Publication xii Types of Users xii Software Dependencies xii Assumptions About Your Locale xiii Demonstration Databases xiii New Features in Dynamic Server, Version xiii Documentation Conventions xiv Typographical Conventions xiv Feature, Product, and Platform Markup xv Example Code Conventions xv Additional Documentation xvi Compliance with Industry Standards xvi IBM Welcomes Your Comments xvi Chapter 1. Performance Basics In This Chapter A Basic Approach to Performance Measurement and Tuning Quick Start for Small-Database User Performance Goals Measurements of Performance Throughput Response Time Cost per Transaction Resource Utilization and Performance Resource Utilization CPU Utilization Memory Utilization Disk Utilization Factors That Affect Resource Utilization Maintenance of Good Performance Chapter 2. Performance Monitoring and the Tools You Use In This Chapter Evaluating the Current Configuration Creating a Performance History The Importance of a Performance History Tools That Create a Performance History Monitoring Database Server Resources Monitoring Resources That Impact CPU Utilization Monitoring Memory Utilization Monitoring Disk I/O Utilization Monitoring Transactions The onlog Utility Using the onstat Utility to Monitor Transactions Using ISA to Monitor Transactions Monitoring Sessions and Queries Monitoring Memory Usage for Each Session Using SET EXPLAIN Chapter 3. Effect of Configuration on CPU Utilization In This Chapter UNIX Configuration Parameters That Affect CPU Utilization Copyright IBM Corp. 1996, 2007 iii

6 UNIX Semaphore Parameters UNIX File-Descriptor Parameters UNIX Memory Configuration Parameters Windows Configuration Parameters That Affect CPU Utilization ONCONFIG File Configuration Parameters and Environment Variables That Affect CPU Utilization Specifying Virtual Processor Class Information By Using the VPCLASS Configuration Parameter Setting the MULTIPROCESSOR Configuration Parameter When Using Multiple CPU VPs Setting the SINGLE_CPU_VP Configuration Parameter When Using One CPU VP Optimizing Access Methods by Using the OPTCOMPIND Configuration Parameter Limiting PDQ Resources in Queries by Using the MAX_PDQPRIORITY Configuration Parameter Limiting the Performance Impact of CPU-Intensive Queries By Using the DS_MAX_QUERIES Configuration Parameter Limiting the Number of PDQ Scan Threads that Can Run Concurrently by Using the DS_MAX_SCANS Configuration Parameter Configuring Poll Threads by Using the NETTYPE Configuration Parameter Enabling Fast Polling by Using the FASTPOLL Configuration Parameter Network Buffer Pools Using the NETTYPE Configuration Parameter in Relation to Network Buffer Pools Enabling Support for Private Network Buffers by Using the IFX_NETBUF_PVTPOOL_SIZE Environment Variable Setting Each Network Buffer Size by Using the IFX_NETBUF_SIZE Environment Variable Virtual Processors and CPU Utilization Adding Virtual Processors Monitoring Virtual Processors CPU Virtual Processor Memory Caches Connections and CPU Utilization Multiplexed Connections MaxConnect for Multiple Connections (UNIX) Chapter 4. Effect of Configuration on Memory Utilization In This Chapter Allocating Shared Memory Resident Portion Virtual Portion Message Portion Configuring UNIX Shared Memory Freeing Shared Memory with onmode -F Configuration Parameters That Affect Memory Utilization Setting the Size of the Buffer Pool, Logical-Log Buffer, and Physical-Log Buffer LOCKS RESIDENT SHMADD and EXTSHMADD SHMTOTAL SHMVIRTSIZE SHMVIRT_ALLOCSEG STACKSIZE Parameters That Affect Memory Caches UDR Cache Data-Dictionary Cache Data-Distribution Cache SQL Statement Cache Prepared Statements and the Statement Cache SQL Statement Cache Configuration Monitoring and Tuning the SQL Statement Cache Session Memory Data-Replication Buffers and Memory Utilization Memory Latches Monitoring Latches with Command-Line Utilities Monitoring Latches with ISA Monitoring Latches with SMI Tables Encrypted Values iv IBM Informix Dynamic Server Performance Guide

7 Chapter 5. Effect of Configuration on I/O Activity In This Chapter Chunk and Dbspace Configuration Direct I/O for Cooked Files Used for dbspace Chunks (UNIX only) Associate Disk Partitions with Chunks Associate Dbspaces with Chunks Place System Catalog Tables with Database Tables Placement of Critical Data Consider Separate Disks for Critical Data Components Consider Mirroring for Critical Data Components Configuration Parameters That Affect Critical Data Configuring Dbspaces for Temporary Tables and Sort Files Creating Temporary Dbspaces DBSPACETEMP Configuration Parameter DBSPACETEMP Environment Variable Estimating Temporary Space PSORT_NPROCS Environment Variable Configuring Sbspaces for Temporary Smart Large Objects Creating Temporary Sbspaces SBSPACETEMP Configuration Parameter Placement of Simple Large Objects Advantage of Blobspaces over Dbspaces Blobpage Size Considerations Parameters That Affect I/O for Smart Large Objects Disk Layout for Sbspaces Configuration Parameters That Affect Sbspace I/O onspaces Options That Affect Sbspace I/O How the Optical Subsystem Affects Performance Environment Variables and Configuration Parameters for the Optical Subsystem STAGEBLOB OPCACHEMAX INFORMIXOPCACHE Table I/O Sequential Scans Light Scans Unavailable Data Configuration Parameters That Affect Table I/O RA_PAGES and RA_THRESHOLD DATASKIP Background I/O Activities Configuration Parameters That Affect Checkpoints Configuration Parameters That Affect Logging Configuration Parameters That Affect Page Cleaning Configuration Parameters That Affect Backup and Restore Configuration Parameters That Affect Rollback and Recovery Configuration Parameters That Affect Data Replication and Auditing LRU Tuning Chapter 6. Table Performance Considerations In This Chapter Placing Tables on Disk Isolating High-Use Tables Placing High-Use Tables on Middle Partitions of Disks Using Multiple Disks Backup-and-Restore Considerations Improving Performance for Nonfragmented Tables and Table Fragments Estimating Table Size Estimating Data Pages Estimating Pages That Simple Large Objects Occupy Managing the Size of First and Next Extents for the tblspace tblspace Managing Sbspaces Contents v

8 Estimating Pages That Smart Large Objects Occupy Improving Metadata I/O for Smart Large Objects Monitoring Sbspaces Changing Storage Characteristics of Smart Large Objects Managing Extents Choosing Table Extent Sizes Monitoring Active Tblspaces Monitoring the Upper Limit on Extents and Extent Interleaving Reclaiming Unused Space Within an Extent Managing Extent Deallocation with the TRUNCATE Keyword Storing Multiple Table Fragments in a Single dbspace Changing Tables Loading and Unloading Tables Dropping Indexes for Table-Update Efficiency Attaching or Detaching Fragments Altering a Table Definition Denormalizing the Data Model to Improve Performance Shortening Rows Expelling Long Strings Splitting Wide Tables Redundant Data Reduce Disk Space Through Additional Rows Per Page In Tables With Variable Length Rows Enabling the Server to Insert Rows Into a Page Chapter 7. Index Performance Considerations In This Chapter Estimating Index Pages Index Extent Sizes Estimating Conventional lndex Pages Estimating Index Pages for Spatial and User-Defined Data Managing Indexes Space Costs of Indexes Time Costs of Indexes Choosing Columns for Indexes Dropping Indexes Creating and Dropping an Index in an Online Environment Circumstances Under Which You Cannot Create or Drop Indexes Online Creating Attached Indexes in an Online Environment Limiting Memory Allocation While Creating Indexes Online by Using the ONLIDX_MAXMEM Configuration Parameter Improving Performance for Index Builds Estimating Memory Needed for Sorting Estimating Temporary Space for Index Builds Storing Multiple Index Fragments in a Single dbspace Improving Performance for Index Checks Indexes on User-Defined Data Types Defining Indexes for User-Defined Data Types Using an Index That a DataBlade Module Provides Choosing Operator Classes for Indexes Chapter 8. Locking In This Chapter Locks Lock Granularity Row and Key Locks Page Locks Table Locks Database Locks Configuring Lock Mode Lock Waits vi IBM Informix Dynamic Server Performance Guide

9 Locks with the SELECT Statement Isolation Level Locking Nonlogging Tables Update Cursors Locks Placed with INSERT, UPDATE, and DELETE Monitoring and Administering Locks Monitoring Locks Configuring and Monitoring the Number of Locks Monitoring Lock Waits and Lock Errors Monitoring Deadlocks Monitoring Isolation That Sessions Use Locks for Smart Large Objects Types of Locks on Smart Large Objects Byte-Range Locking Lock Promotion Dirty Read and Smart Large Objects Chapter 9. Fragmentation Guidelines In This Chapter Planning a Fragmentation Strategy Setting Fragmentation Goals Examining Your Data and Queries Considering Physical Fragmentation Factors Designing a Distribution Scheme Choosing a Distribution Scheme Designing an Expression-Based Distribution Scheme Suggestions for Improving Fragmentation Fragmenting Indexes Attached Indexes Detached Indexes Restrictions on Indexes for Fragmented Tables Fragmenting Temporary Tables Using Distribution Schemes to Eliminate Fragments Fragmentation Expressions for Fragment Elimination Query Expressions for Fragment Elimination Effectiveness of Fragment Elimination Improving the Performance of Attaching and Detaching Fragments Improving ALTER FRAGMENT ATTACH Performance Improving ALTER FRAGMENT DETACH Performance Monitoring Fragment Use Using the onstat Utility Using SET EXPLAIN Chapter 10. Queries and the Query Optimizer In This Chapter The Query Plan Access Plan Join Plan Example of Query-Plan Execution Query Plans that Include an Index Self-Join Path Query Plan Evaluation Report that Shows the Query Plan Chosen by the Optimizer Sample Query Plan Reports Factors That Affect the Query Plan Statistics Held for the Table and Index Filters in the Query Indexes for Evaluating a Filter Effect of PDQ on the Query Plan Effect of OPTCOMPIND on the Query Plan Effect of Available Memory on the Query Plan Contents vii

10 Time Costs of a Query Memory-Activity Costs Sort-Time Costs Row-Reading Costs Sequential Access Costs Nonsequential Access Costs Index Lookup Costs In-Place ALTER TABLE Costs View Costs Small-Table Costs Data-Mismatch Costs Encrypted-Value Costs GLS Functionality Costs Network-Access Costs SQL Within SPL Routines SQL Optimization Execution of an SPL Routine UDR Cache Trigger Execution Performance Implications for Triggers Chapter 11. Optimizer Directives In This Chapter What Optimizer Directives Are Optimizer Directives That Are Embedded in Queries External Optimizer Directives Reasons to Use Optimizer Directives Preparation for Using Directives Guidelines for Using Directives Types of Directives That Are Included in SQL Statements Access-Method Directives Join-Order Directives Join-Plan Directives Optimization-Goal Directives Example with Directives EXPLAIN Directives Configuration Parameters and Environment Variables for Optimizer Directives Optimizer Directives and SPL Routines Forcing Reoptimization to Avoid an Index and Previously Prepared Statement Problem If AUTO_REPREPARE Is Not Enabled Using External Optimizer Directives Creating and Saving External Directives Enabling External Directives Deleting External Directives Chapter 12. Parallel Database Query In This Chapter What Parallel Database Query (PDQ) Is Structure of a PDQ Query Database Server Operations That Use PDQ Parallel Delete Parallel Inserts Parallel Index Builds Parallel User-Defined Routines Hold Cursors That Use PDQ SQL Operations That Do Not Use PDQ Update Statistics SPL Routines and Triggers Correlated and Uncorrelated Subqueries OUTER Index Joins viii IBM Informix Dynamic Server Performance Guide

11 Remote Tables Memory Grant Manager Allocating Resources for Parallel Database Queries Limiting the Priority of DSS Queries Adjusting the Amount of Memory Limiting the Number of Concurrent Scans Limiting the Maximum Number of Queries Managing Applications Using SET EXPLAIN Using OPTCOMPIND Using SET PDQPRIORITY User Control of Resources DBA Control of Resources Monitoring PDQ Resources Using the onstat Utility Using SET EXPLAIN Chapter 13. Improving Individual Query Performance In This Chapter Using a Dedicated Test System Displaying the Query Plan Improving Filter Selectivity Filters with User-Defined Routines Avoiding Certain Filters Using Join Filters and Post-Join Filters Updating Statistics When They Are Not Generated Automatically Updating the Number of Rows Dropping Data Distributions Creating Data Distributions Updating Statistics for Join Columns Updating Statistics for Columns with User-Defined Data Types Using Update Statistics With Very Large Databases Displaying Distributions Improving the Performance of UPDATE STATISTICS Improving Performance with Indexes Replacing Autoindexes with Permanent Indexes Using Composite Indexes Using Indexes for Data Warehouse Applications Configuring B-Tree Scanner Information to Improve Transaction Processing Determining the Amount of Free Space in an Index Page Improving Performance of Distributed Queries Buffering Data Transfers for a Distributed Query Displaying a Query Plan for a Distributed Query Improving Sequential Scans Enabling View Folding to Improve Query Performance Reducing the Impact of Join and Sort Operations Avoiding or Simplifying Sort Operations Using Parallel Sorts Using Temporary Tables to Reduce Sorting Scope More Memory for Queries with Hash Joins, Aggregates, and Other Memory-Intensive Elements Optimizing User-Response Time for Queries Optimization Level Optimization Goal Optimizing Queries for User-Defined Data Types Parallel UDRs Selectivity and Cost Functions User-Defined Statistics for UDTs Negator Functions SQL Statement Cache When to Use the SQL Statement Cache Using the SQL Statement Cache Contents ix

12 Monitoring Memory Usage for Each Session Monitoring Usage of the SQL Statement Cache Monitoring Sessions and Threads Using Command-Line Utilities Using ON-Monitor to Monitor Sessions (UNIX) Using ISA to Monitor Sessions Using SMI Tables Monitoring Transactions Displaying Transactions with onstat -x Displaying Locks with onstat -k Displaying User Sessions with onstat -u Displaying Sessions Executing SQL Statements Chapter 14. The onperf Utility on UNIX In This Chapter Overview of the onperf Utility Basic onperf Functions The onperf Tools Requirements for Running onperf Starting and Exiting onperf The onperf User Interface Graph Tool Query-Tree Tool Status Tool Activity Tools Ways to Use onperf Routine Monitoring Diagnosing Sudden Performance Loss Diagnosing Performance Degradation The onperf Metrics Database Server Metrics Disk-Chunk Metrics Disk-Spindle Metrics Physical-Processor Metrics Virtual-Processor Metrics Session Metrics Tblspace Metrics Fragment Metrics Appendix A. Case Studies and Examples A-1 Appendix B. Accessibility B-1 Accessibility features for IBM Informix Dynamic Server B-1 Accessibility Features B-1 Keyboard Navigation B-1 Related Accessibility Information B-1 IBM and Accessibility B-1 Notices C-1 Trademarks C-3 Index X-1 x IBM Informix Dynamic Server Performance Guide

13 Introduction In This Introduction xi About This Publication xi Topics Beyond the Scope of This Publication xii Types of Users xii Software Dependencies xii Assumptions About Your Locale xiii Demonstration Databases xiii New Features in Dynamic Server, Version xiii Documentation Conventions xiv Typographical Conventions xiv Feature, Product, and Platform Markup xv Example Code Conventions xv Additional Documentation xvi Compliance with Industry Standards xvi IBM Welcomes Your Comments xvi In This Introduction About This Publication This introduction provides an overview of the information in this publication and describes the conventions it uses. This publication provides information about how to configure and operate IBM Informix Dynamic Server to improve overall system throughput and to improve the performance of SQL queries. The publication includes information on performance tuning issues and methods that are relevant to daily database server administration and query execution. Performance measurement and tuning encompass a broad area of research and practice and can involve information beyond the scope of this publication. Information in this publication can help you perform the following tasks: v Monitor system resources that are critical to performance v Identify database activities that affect these critical resources v Identify and monitor queries that are critical to performance v Use the database server utilities (especially onperf, ISA and onstat) for performance monitoring and tuning v Eliminate performance bottlenecks by: Balancing the load on system resources Adjusting the configuration parameters or environment variables of your database server Adjusting the arrangement of your data Allocating resources for decision-support queries Creating indexes to speed up retrieval of your data In addition, this publication contains the full description of the onperf utility. Copyright IBM Corp. 1996, 2007 xi

14 Topics Beyond the Scope of This Publication Attempts to balance the workload often produce a succession of moderate performance improvements. Sometimes the improvements are dramatic. However, in some situations a load-balancing approach is not enough. The following types of situations might require measures beyond the scope of this publication: v Application programs that require modification to make better use of database server or operating-system resources v Applications that interact in ways that impair performance v A host computer that might be subject to conflicting uses v A host computer with capacity that is inadequate for the evolving workload v Network performance problems that affect client/server or other applications No amount of database tuning can correct these situations. Nevertheless, they are easier to identify and resolve when the database server is configured properly. Important: Although broad performance considerations also include reliability and data availability as well as improved response time and efficient use of system resources, this publication discusses only response time and system resource use. For discussions of improved database server reliability and data availability, see information about switchover, mirroring, and high availability in your IBM Informix Dynamic Server Administrator's Guide. For information about backup and restore, see the IBM Informix Backup and Restore Guide. Types of Users This publication is written for the following users: Software v Database administrators v Database server administrators v Database-application programmers v Performance engineers This publication assumes that you have the following background: v A working knowledge of your computer, your operating system, and the utilities that your operating system provides v Some experience working with relational databases or exposure to database concepts v Some experience with computer programming v Some experience with database server administration, operating-system administration, or network administration If you have limited experience with relational databases, SQL, or your operating system, see the IBM Informix Dynamic Server Getting Started Guide for your database server for a list of supplementary titles. Dependencies This publication assumes that you are using IBM Informix Dynamic Server, Version xii IBM Informix Dynamic Server Performance Guide

15 Assumptions About Your Locale IBM Informix products can support many languages, cultures, and code sets. All the information related to character set, collation, and representation of numeric data, currency, date, and time is brought together in a single environment, called a Global Language Support (GLS) locale. This manual assumes that you use the U.S English locale as the default locale. The default is en_us (ISO ) on UNIX platforms or en_us.1252 (Microsoft 1252) for Windows environments. This locale supports U.S. English format conventions for date, time, and currency, and also supports the ISO or Microsoft 1252 code set, which includes the ASCII code set plus many 8-bit characters such as é, è, and ñ. If you plan to use nondefault characters in your data or your SQL identifiers, or if you want to conform to the nondefault collation rules of character data, you need to specify the appropriate nondefault locale. For instructions on how to specify a nondefault locale, additional syntax, and other considerations related to GLS locales, see the IBM Informix GLS User's Guide. Demonstration Databases The DB Access utility, which is provided with your IBM Informix database server products, includes one or more of the following demonstration databases: v The stores_demo database illustrates a relational schema with information about a fictitious wholesale sporting-goods distributor. Many examples in IBM Informix manuals are based on the stores_demo database. v The superstores_demo database illustrates an object-relational schema. The superstores_demo database contains examples of extended data types, type and table inheritance, and user-defined routines. For information about how to create and populate the demonstration databases, see the IBM Informix DB Access User's Guide. For descriptions of the databases and their contents, see the IBM Informix Guide to SQL: Reference. The scripts that you use to install the demonstration databases reside in the $INFORMIXDIR/bin directory on UNIX platforms and in the %INFORMIXDIR%\bin directory in Windows environments. New Features in Dynamic Server, Version Version includes new features that enhance the functionality of the database server and make it easier to use. The following table provides information about the new features for IBM Informix Dynamic Server, Version 11.10, which this publication covers. For a comprehensive list of new features for this release, see the IBM Informix Getting Started Guide. This topic lists new features relevant to this publication. New Features Reference The RTO_SERVER_RESTART configuration parameter that enables you to set the amount of time, in seconds, that Dynamic Server has to recover from a problem after you restart Dynamic Server and bring it into online or quiescent mode RTO_SERVER_RESTART on page 5-38 Introduction xiii

16 New Features Reference Support of limited transaction blocking (referred to as nonblocking checkpoints) RTO_SERVER_RESTART on page 5-38 and the IBM Informix Dynamic Server Administrator's Guide This allows an application to process transactions while a checkpoint is being processed. This feature eliminates fuzzy checkpoints. In prior versions of Informix Dynamic Server, in order to reduce the transaction blocking time of a checkpoint, LRU flushing was tuned to be very aggressive. Now, LRU flushing can be less aggressive. The ability to use SQL to fold derived tables into parent queries Support for the creation of multiple BEFORE, FOR EACH ROW and AFTER triggers for the same INSERT, UPDATE, DELETE, or SELECT event on a table or view, and support for a new UDR type, called a trigger routine SQL operations that explicitly or implicitly create a B-tree index on a non-opaque column or set of columns automatically calculate distributions on the lead indexed column of the table A configuration parameter that enables or disables the inclusion of query statistics in SET EXPLAIN output A new LAST COMMITTED keyword option to the SET ISOLATION COMMITTED READ statement to reduce the risk of locking conflicts when attempting to read a table; and a new configuration parameter that specifies whether the database server uses the last committed version of the data when a lock occurs Functionality for improving concurrency with private memory caches, and a configuration parameter that you can use to specify information for a memory cache Derived Tables Folded into Parent Queries on page Trigger Execution on page see the IBM Informix Guide to SQL: Syntax Updating Statistics on All Participating Tables on page 9-22 Query Statistics Section Provides Performance Debugging Information on page Committed Read Isolation on page 8-6 CPU Virtual Processor Memory Caches on page 3-20 Improved performance for cooked files with direct I/O Direct I/O for Cooked Files Used for dbspace Chunks (UNIX only) on page 5-3 Automatic re-compilation of prepared statements Forcing Reoptimization to Avoid an Index and Previously Prepared Statement Problem If AUTO_REPREPARE Is Not Enabled on page Documentation Conventions This section describes the following conventions, which are used in the product documentation for IBM Informix Dynamic Server: v Typographical conventions v Feature, product, and platform conventions v Syntax diagrams v Command-line conventions v Example code conventions Typographical Conventions This publication uses the following conventions to introduce new terms, illustrate screen displays, describe command syntax, and so forth. xiv IBM Informix Dynamic Server Performance Guide

17 Convention Meaning KEYWORD Keywords of SQL, SPL, and some other programming languages appear in uppercase letters in a serif font. italics Within text, new terms and emphasized words appear in italics. Within syntax and code examples, variable values that you are to specify appear in italics. boldface Names of program entities (such as classes, events, and tables), environment variables, file names, path names, and interface elements (such as icons, menu items, and buttons) appear in boldface. monospace Information that the product displays and information that you enter appear in a monospace typeface. KEYSTROKE Keys that you are to press appear in uppercase letters in a sans serif font. > This symbol indicates a menu item. For example, Choose Tools > Options means choose the Options item from the Tools menu. Feature, Product, and Platform Markup Feature, product, and platform markup identifies paragraphs that contain feature-specific, product-specific, or platform-specific information. Some examples of this markup follow: Dynamic Server Identifies information that is specific to IBM Informix Dynamic Server End of Dynamic Server Windows Only Identifies information that is specific to the Windows operating system End of Windows Only This markup can apply to one or more paragraphs within a section. When an entire section applies to a particular product or platform, this is noted as part of the heading text, for example: Table Sorting (Windows) Example Code Conventions Examples of SQL code occur throughout this publication. Except as noted, the code is not specific to any single IBM Informix application development tool. If only SQL statements are listed in the example, they are not delimited by semicolons. For instance, you might see the code in the following example: CONNECT TO stores_demo... DELETE FROM customer WHERE customer_num = COMMIT WORK DISCONNECT CURRENT Introduction xv

18 To use this SQL code for a specific product, you must apply the syntax rules for that product. For example, if you are using DB Access, you must delimit multiple statements with semicolons. If you are using an SQL API, you must use EXEC SQL at the start of each statement and a semicolon (or other appropriate delimiter) at the end of the statement. Tip: Ellipsis points in a code example indicate that more code would be added in a full application, but it is not necessary to show it to describe the concept being discussed. For detailed directions on using SQL statements for a particular application development tool or SQL API, see the documentation for your product. Additional Documentation You can view, search, and print all of the product documentation from the IBM Informix Dynamic Server information center on the Web at publib.boulder.ibm.com/infocenter/idshelp/v111/index.jsp. For additional documentation about IBM Informix Dynamic Server and related products, including release notes, machine notes, and documentation notes, go to the online product library page at pubs/library/. Alternatively, you can access or install the product documentation from the Quick Start CD that is shipped with the product. Compliance with Industry Standards The American National Standards Institute (ANSI) and the International Organization of Standardization (ISO) have jointly established a set of industry standards for the Structured Query Language (SQL). IBM Informix SQL-based products are fully compliant with SQL-92 Entry Level (published as ANSI X ), which is identical to ISO 9075:1992. In addition, many features of IBM Informix database servers comply with the SQL-92 Intermediate and Full Level and X/Open SQL Common Applications Environment (CAE) standards. IBM Welcomes Your Comments We want to know about any corrections or clarifications that you would find useful in our publications, which will help us improve future versions. Include the following information: v The name and version of the publication that you are using v Section and page number v Your suggestions about the publication Send your comments to us at the following address: docinf@us.ibm.com This address is reserved for reporting errors and omissions in our documentation. For immediate help with a technical problem, contact IBM Technical Support. For instructions, see the IBM Informix Technical Support website at We appreciate your suggestions. xvi IBM Informix Dynamic Server Performance Guide

19 Chapter 1. Performance Basics In This Chapter A Basic Approach to Performance Measurement and Tuning Quick Start for Small-Database User Performance Goals Measurements of Performance Throughput Throughput Measurement Standard Throughput Benchmarks Response Time Response Time and Throughput Response-Time Measurement Cost per Transaction Resource Utilization and Performance Resource Utilization CPU Utilization Memory Utilization Disk Utilization Factors That Affect Resource Utilization Maintenance of Good Performance In This Chapter This publication contains information on performance tuning issues and methods that are relevant to daily database server administration and query execution. Performance measurement and tuning encompass a broad area of research and practice and can involve information beyond the scope of this publication. For more information about the types of information contained in the publication and the topics that are beyond the scope of this publication, see About This Publication on page xi. For a description of the database server parallel processing and the applications that use the database server, see the IBM Informix Dynamic Server Getting Started Guide. This chapter does the following: v Describes a basic approach for performance measurement and tuning v Provides guidelines for a quick start to obtain acceptable initial performance on a small database v Describes roles in maintaining good performance v Lists topics that are not covered in this publication A Basic Approach to Performance Measurement and Tuning Early indications of a performance problem are often vague; users might report that the system seems sluggish. Users might complain that they cannot get all their work done, that transactions take too long to complete, that queries take too long to process, or that the application slows down at certain times during the day. To determine the nature of the problem, you must measure the actual use of system resources and evaluate the results. Users typically report performance problems in the following situations: Copyright IBM Corp. 1996,

20 v Response times for transactions or queries take longer than expected. v Transaction throughput is insufficient to complete the required workload. v Transaction throughput decreases. To maintain optimum performance for your database applications, develop a plan for measuring system performance, making adjustments to maintain good performance and taking corrective measures when performance degrades. Regular, specific measurements can help you to anticipate and correct performance problems. By recognizing problems early, you can prevent them from affecting users significantly. An iterative approach to optimizing database server performance is recommended. If repeating the steps found in the following list does not produce the desired improvement, insufficient hardware resources or inefficient code in one or more client applications might be causing the problem. To optimize performance: 1. Establish performance objectives. 2. Take regular measurements of resource utilization and database activity. 3. Identify symptoms of performance problems: disproportionate utilization of CPU, memory, or disks. 4. Tune the operating-system configuration. 5. Tune the database server configuration. 6. Optimize the chunk and dbspace configuration, including placement of logs, sort space, and space for temporary tables and sort files. 7. Optimize the table placement, extent sizing, and fragmentation. 8. Improve the indexes. 9. Optimize background I/O activities, including logging, checkpoints, and page cleaning. 10. Schedule backup and batch operations for off-peak hours. 11. Optimize the implementation of the database application. 12. Repeat steps 2 through 11. Quick Start for Small-Database User This section is for users who have a small database with each table residing on only one disk and using only one CPU virtual processor. To achieve acceptable initial performance on a small database: 1. Generate statistics of your tables and indexes to provide information to the query optimizer to enable it to choose query plans with the lowest estimated cost. These statistics are a minimum starting point to obtain good performance for individual queries. For guidelines, see Updating Statistics When They Are Not Generated Automatically on page To see the query plan that the optimizer chooses for each query, see Displaying the Query Plan on page If you want a query to execute in parallel execution, you must turn on the Parallel Database Query (PDQ) feature. Without table fragmentation across multiple disks, parallel scans do not occur. With only one CPU virtual processor, parallel joins or parallel sorts do not 1-2 IBM Informix Dynamic Server Performance Guide