This article is part 2 in the series that focuses on improving performance in Db2 Warehouse databases. The first part provided some background information and discussed some basic concepts relevant to query optimization in the context of the Db2 Warehouse column engine. It also covered reading of the query explain plan that provides query execution plan information to help with tuning. The rest of the article was devoted to cardinality estimation. Better estimations of cardinality or the number of rows flowing through the operators during query execution allows the optimizer to cost and choose better query execution plans.
The ”Improving Performance in Your Data Warehouse” series of articles intends to cover the following (Part 3 and Part 4 are yet to be written and the topics could change):
Part 1 : Optimizer and Db2 Warehouse Basics + How to Improve Cardinality Estimates
( https://www.idug.org/p/bl/et/blogid=278&blogaid=779 )
Part 2 : Identifying Costly Operations + Improving Scans + Improving Joins
Part 3 : Improving Aggregation + Improving SORT (Future Article)
Part 4 : Rewriting Queries To Improve Performance + Miscellaneous Tips and Tricks To Improve Performances (Future Article)
Click here to read the full article. (IDUG login required).