DB2 integration with Domino started with 7.0.2 release and has improved dramatically since then. Under 7.0.2 it was available only by requesting it. With 8.0, it's a free add-on to the server. The db2 version supported is v9.1 for Domino 8, while v9.5 can be used.
There are numerous articles, including the Admin help, on the installation of DB2 and the DB2 Access Server.
This article will deal with what a developer can do with a DB2 enabled server.
There are 2 additional design elements available for DB2 enabled databases, the query view and DB2 Access Views. These design elements are only available if the database is DB2 enabled. Since templates are not store as DB2 enabled, you couldn't see the new design elements. By adding "Designer_ShowDavQv=1" to the workstation's Notes.ini, you can see the new design elements. This entry is not needed for the current Notes 8.5 beta2, it shows the design elements.