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Blog Entry
IDUG Tech Talk: The ABCs of Filter Factors (aka Selectivity)

Tuning of SQL queries requires understanding why DB2 chose a particular access path and determining whether or not that access path should perform as expected. The key to this is understanding what filter factors are, how they are used by the Optimizer and how to get DB2 to better estimate them ...

Joe Geller's profile image

Blog Entry
The (unknown) benefits of FETCH FIRST in DB2 for z/OS SQL

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...

Terry Purcell's profile image

Blog Entry
IDUG Tech Talk. Access Paths for DB2 10.5 for LUW Column Based Tables by Mark Gillis

One of the selling points of DB2 10.5 and the Columnar options is that existing row-based tables can be converted to column-based tables and will be accessed by DB2 seamlessly and with no extra effort from the DBA. All well and good, and the performance should be much better, but what if it’s...


Blog Entry
How to Avoid Dramatic Access Path Changes in DB2 for z/OS Dynamic SQL (or at Least Fix Them Quickly)

By Kurt Struyf, Lone Star Consulting This article is based on a recent tuning engagement at a customer site and describes the countermeasures that were enacted to restore system performance. Those countermeasures include a daily process to establish an access path baseline and sample jobs...

Kurt Struyf's profile image

Library Entry
[A08] DB2 11 Query Performance Optimization: Statistics Profiles and Collection

DB2 11 significantly improves query performance and database administration through enhancements to catalog statistics and optimization profiles. Statistics collection have been improved in DB2 11 to make them easier to use and maintain. Their capabilities have also been extended to collect...

EU13A08.pdf


Blog Entry
IDUG Tech Talk - DB2 10 for z/OS Optimization Enhancements

Terry Purcell of the IBM SVL Optimization Team recorded his IDUG presentation introducing the query optimization enhancements that were delivered with DB2 10 for z/OS. Terry goes into detail of each enhancement and explains when each optimization improvement can and will be applied. Check it out...


Blog Entry
Potential SQL Performance Improvements in DB2 11 ESP for z/OS

Potential SQL Performance Improvements in DB2 11 for z/OS By Daniel L Luksetich, IDUG DB2 11 White Paper Editorial Committee As with any new release of DB2 for z/OS there comes a host of SQL performance improvements. Some of these you get straight away, some with a bind or next prepare...



Library Entry
The DB2 Linux, Unix, Windows Query Optimizer

In this presentation John Hornibrook takes viewers into a deep dive into the workings of the DB2 optimizer.

6e0r5g725m3855.flv


Library Entry
The DB2 Linux, Unix, Windows Query Optimizer

In this presentation John Hornibrook takes viewers into a deep dive into the workings of the DB2 optimizer.

6e0r5g725m3855.flv