Front cover DB2 Cube Views A Primer Introduce DB2 Cube Views as a key player in the OLAP world Understand cube models, cubes and optimization Improve your metadata flow and speed up queries Corinne Baragoin Geetha Balasubramaniam Bhuvana Chandrasekharan Landon DelSordo Jan B Lillelund Julie Maw Annie Neroda Paulo Pereira Jo A Ramos ibm.com/redbooks International Technical Support Organization DB2 Cube Views: A Primer September 2003 SG24-7002-00 Note: Before using this information and the product it supports, read the information in “Notices” on page xxix. First Edition (September 2003) This edition applies to IBM DB2 Universal Database V8.1 Fixpack 2+, IBM DB2 Cube Views V8.1, IBM DB2 Office Connect Analytics Edition V4.0, IBM QMF For Windows V7.2f, Ascential MetaStage V7.0, Meta Integration Model Bridge V3.1, IBM DB2 OLAP Server V8.1, Cognos Series 7, BusinessObjects Enterprise 6, and MicroStrategy V7.2.3. Note: We recommend that you consult the product documentation or follow-on versions of this redbook for more current information. © Copyright International Business Machines Corporation 2003. All rights reserved. Note to U.S. Government Users Restricted Rights -- Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp. Contents Figures . .xi Tables . xxv Examples. .xxvii Notices . xxix Trademarks . xxx Preface . xxxi The team that wrote this redbook. .xxxii Become a published author . xxxv Comments welcome. xxxv Part 1. Understand DB2 Cube Views. 1 Chapter 1. An OLAP-aware DB2. 3 1.1 Business Intelligence and OLAP introduction . 4 1.1.1 Online Analytical Processing. 5 1.1.2 Metadata . 8 1.2 DB2 UDB V8.1 becomes OLAP-aware . 9 1.3 Challenges faced by DBA’s in an OLAP environment. 11 1.3.1 Manage the flow of metadata . 11 1.3.2 Optimize and manage custom summary tables . 11 1.3.3 Optimize MOLAP database loading . 12 1.3.4 Enhance OLAP queries performance in the relational database . 13 1.4 How DB2 can help. 13 1.4.1 Efficient multidimensional model: cube model . 14 1.4.2 Summary tables optimization: Optimization Advisor . 15 1.4.3 Interfaces . 17 1.5 Metadata bridges to back-end and front-end tools . 19 Chapter 2. DB2 Cube Views: scenarios and benefits . 21 2.1 What can DB2 Cube Views do for you? . 22 2.2 Feeding metadata into DB2 Cube Views . 29 2.2.1 Feeding DB2 Cube Views from back-end tools . 31 2.2.2 Feeding DB2 Cube Views from front-end tools. 34 2.2.3 Feeding DB2 Cube Views from scratch . 36 2.3 Feeding front-end tools from DB2 Cube Views . 39 © Copyright IBM Corp. 2003. All rights reserved. iii 2.3.1 Supporting MOLAP tools with DB2 Cube Views . 40 2.3.2 Supporting ROLAP tools with DB2 Cube Views . 46 2.3.3 Supporting HOLAP tools with DB2 Cube Views . 50 2.3.4 Supporting bridgeless ROLAP tools with DB2 Cube Views . 54 2.4 Feeding Web services from DB2 Cube Views . 56 2.4.1 A scenario . 57 2.4.2 Flow and components . 57 2.4.3 Benefits . 58 Part 2. Build and optimize the DB2 Cube Model . 61 Chapter 3. Building a cube model in DB2 . 63 3.1 What are the data schemas that can be modeled?. 64 3.1.1 Star schemas . 64 3.1.2 Snowflakes . 66 3.1.3 Star and snowflakes characteristics . 67 3.2 Cube model notion and terminology . 67 3.2.1 Measures and facts. 68 3.2.2 Attributes . 70 3.2.3 Dimensions . 71 3.2.4 Hierarchies . 73 3.2.5 Attribute relationships . 76 3.2.6 Joins . 77 3.2.7 In a nutshell: cube model and cubes. 79 3.3 Building cube models using the OLAP Center . 81 3.3.1 Planning for building a cube model . 85 3.3.2 Preparing the DB2 relational database for DB2 Cube Views . 86 3.3.3 Building the cube model by import . 87 3.3.4 Building a cube model with Quick Start wizard . 91 3.3.5 Creating a basic complete cube model from scratch . 92 3.4 Enhancing a cube model. 118 3.4.1 Based on end-user analytics requirements. 119 3.4.2 Based on Optimization Advisor and MQT usage . 122 3.5 Backup and recovery. 122 3.6 Summary . 124 Chapter 4. Using the cube model for summary tables optimization . 125 4.1 Summary tables and optimization requirements . 126 4.2 How cube model influences summary tables and query performance . 127 4.3 MQTs: a quick overview . 131 4.3.1 MQTs in general . 132 4.3.2 MQTs in DB2 Cube Views . 134 4.4 What you need to know before optimizing . 136 4.4.1 Get at least a cube model and one cube defined . 136 iv DB2 Cube Views: A Primer 4.4.2 Define referential integrity or informational constraints . 136 4.4.3 Do you know or have an idea of the query type? . 143 4.4.4 Understand how Optimization Advisor uses cube model/cube . 149 4.5 Using the Optimization Advisor . 152 4.5.1 How does the wizard work . 152 4.5.2 Check your cube model . 154 4.5.3 Run the Optimization Advisor . 157 4.5.4 Parameters for the Optimization Advisor . 160 4.6 Deploying Optimization Advisor MQTs . 169 4.6.1 What SQL statements are being run?. 172 4.6.2 Are the statements using the MQTs? . 173 4.6.3 How deep in the hierarchies do the MQTs go?. 178 4.6.4 Check the DB2 parameters. 181 4.6.5 Is the query optimization level correct?. 185 4.7 Optimization Advisor and cube model interactions . 185 4.7.1 Optimization Advisor recommendations . 187 4.7.2 Query to the top of the cube . 189 4.7.3 Querying a bit further down the cube . 191 4.7.4 Moving towards the middle of the cube. 194 4.7.5 Visiting the bottom of the cube . 197 4.8 Performance considerations . 197 4.9 Further steps in MQT maintenance. 198 4.9.1 Refresh DEFERRED option . 199 4.9.2 Refresh IMMEDIATE option . 200 4.9.3 Refresh DEFERRED versus refresh IMMEDIATE . 201 4.9.4 INCREMENTAL refresh versus FULL refresh. ..