DB2 for OS/390 V5 vs. V6 outer join performance

The outer join operation is one of the most frequently used operations in a relational database management system. It becomes even more important in data warehouse and business intelligence applications. The processing of outer join of very large relations is a very costly operation. Therefore, a lot of effort has been expended in the development and implementation of optimization techniques to improve the performance of outer join. In this paper, the outer join optimization techniques implemented in DB2 UDB for OS/390 V6 (further reference as DB2 V6) are described and the efficiency is measured in a real world workload.