With the SQL OLAP RANK and DENSE_RANK functions being around for a while in SQL programming, it is quite easy to query for the TOP XX from data.
You can create profiles to selectively control groups of distributed (DBAT) threads and connections, set thresholds for query acceleration (not covered in this article) or provide override properties to model your test subsystem to reflect the computing power of your production environment.
Whenever a performance problem arises, the database takes the blame, but is that really true? This article will provide a hand's on, step by step approach to determine where the problem is. "Guilty Until Proven Innocent"
In Part 1, I talked about some of the first steps that a developer should go through when it comes to tuning queries. In this article, I will go through the initial steps in evaluating a SQL query using the Db2 explain output.
Locking and latching are both key mechanisms employed by relational database management systems to ensure data integrity, consistency, and the serialization of resources. In the Db2 for z/OS IRLM manages the locks, but both Db2 and IRLM have internal latches.