Playing with cardinality and selectivity on predicates is not a common trick, though Joe Geller, David Simpson and Tony Andrews demystify it so that you can start playing with its intricacies and give a boost to the Optimizer.
In 2007, Db2 Version 9 introduced decimal floating point (DECFLOAT) as a new SQL data type. Since then, the storage and data manipulation of DECFLOAT(16) and DECFLOAT(34) data types have been supported. But what about DECFLOAT performance? And performance improvements of this datatype?
Let’s start this discussion candidly – I am a big fan of the FETCH FIRST n ROWS ONLY clause coded in a SQL statement. That assertion will require some clarification, since there are some valid use cases, and others that make little sense. Regardless, I will try not to over-complicate the discussion.
By now, most DB2 for LUW users have probably heard about the release of DB2 11.1 that became available in June of this year. In this article I’d like to provide more information on some performance optimizations in DB2 11.1 that will benefit queries accessing both row and column-organized tables.
There has been quite a bit of attention paid to the access path stability features of DB2 for z/OS since they first appeared in DB2 9. Enhancements have followed in each subsequent release. This article will discuss these features.