Do you want to keep a database on a mobile device? Or are you running a terabyte-sized warehouse? The requirements are then probably different in terms of hardware and software. The good news is there is a developerWorks article describing the different DB2 versions available, ranging from DB2 Everyplace to the full-fledged DB2 Enterprise Server Edition and the different feature packs.
Tell me something cool about this article
For each of the discussed versions there is a section "Tell me something coll running on...". It shows how an IBM customer is using that specific version of DB2.