Edited 12/13/2017 to correct image and details about the database heap.
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.
Edited 11/13/2014 to be more specific about coordinator agents.
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 proper use of constraints.
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 multiple small parts, but that if one of those parts fails, then the transaction as a whole must also fail to have made any changes to the data. This concept is especially critical in relational databases which may be normalized into many smaller tables, which leads to a transaction consisting of more than just a single update in a single location.