Category: DB2 Internals

7

Reclaimable Table Spaces

In DB2 9.7, IBM changed the format of table spaces to be “reclaimable”. This has a ton of advantages, but conversion is ridiculously painful. Why Was the Format Changed? Previously, row addresses (referenced in indexes) were relative to the beginning of the table space. This has a number of implications, the main one being that if tables are moved within...

3

Customizing MONREPORT … or not

If you’re not familiar with MONREPORT, see my DB2 Basics entry on MONREPORT first. Most of the references I’ve seen to customizing the MONREPORT module basically say “get the code out of the database, modify it, and deploy it”. (see IBM DB2 Knowledge Center Entry on Customizing the MONREPORT module reports) I have found this rather frustrating when I’ve run...

15

DB2 Internals: Simple Query Processing

Edited 11/13/2014 to be more specific about coordinator agents. This is the first in a series of blog entries talking about DB2 internals. I have no intimate knowledge from IBM of how DB2 works internally, just years of watching presentations about the internals and doing my best to understand what DB2 is doing to inform my actions and decisions as...

1

Informational Constraints – Benefits and Drawbacks

One of the most frustrating things a DBA can experience is troubleshooting due to bad data. The client is upset because rows are missing or incorrect data is returned.  The client facing web front end could be displaying gobilty-gook because the data retrieved makes no sense. Resources and energy are burned because of an issue is easily solved with the...

15

What does a Commit mean in DB2?

What a Commit is Database management systems have the concept of a commit. This concept has to do with grouping sets of actions together such that they all succeed or fail as a group. This represents the A in the famous ACID properties of a transaction system. The A stands for Atomicity – meaning that a transaction may consist of...