In this article, inspired from his presentation in IDUG EMEA 2019, Pawel Hryb talks on possibilities and strategies when doing complex SQL tuning in Db2 for z/OS: Where to begin, how to dissect a complex query, sources of information to try and how to proceed when you need a deeper investigation.
In this article, Brian Laube shows how we can solve a real-life performance problem by copying access path information from one environment to another one and then using it as an optimization hint.
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.