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Summary

The DB2 optimizer is an advanced, cost-based optimizer and normally chooses very efficient access plans. However, to enable the optimizer to choose an efficient plan, ensure that:

  • The tables are indexed correctly for the workload

  • The table and index statistics are current

  • The optimization level is set correctly based on the workload

  • Parallelism is enabled only if the workload will benefit from it



    		IBM Press Series?Information Management
    		About Prentice Hall Professional Technical Reference
    		Foreword
    		Preface
    		Chapter 1. Data Storage
    		Chapter 2. Data Manipulation
    		Chapter 3. Database Availability
    		Chapter 4. Database Security
    		Chapter 5. Multi-Dimensional Clustering
    		Chapter 6. The DB2 Optimizer
    		Joining in DB2 UDB
    		Materialized Query Tables
    		Understanding DB2 Query Access Plans
    		Summary
    		Chapter 7. Federated Database Access
    		Chapter 8. Performance Tuning
    		Chapter 9. Database Communications
    		Chapter 10. Performance Tuning Examples
    		Appendix A. Useful DB2 Commands
    		Appendix B. parseSQL.pl
    		Appendix C. exfmtDIF.pl
    		Appendix D. Comparing Index Advisor Recommended Indexes with Existing Indexes
    		Appendix E. Configuration Parameters That Can Be Changed Online
    		Appendix F. Explain Tools
    		Appendix G. Starting and Stopping a DB2 Instance
    		Appendix H. LDAP Integration in DB2 UDB Using Microsoft Active Directory
    		Appendix I. Tuning DB2 UDB in the IBM LDAP Environment
    		Appendix J. DB2 Support Information
    		Appendix K. DB2 Connect Implementation
    		Appendix L. Sample Questions
    		Appendix M. Answers to Sample Questions
    		About the CD-ROM
    		Article