In Notes/Domino 7, you have the ability to use a DB2 back-end to provide robust query capabilities across multiple Notes databases. There is some work required to set this up:
DB2 must be installed. This does not come with Domino; it is a separate install.
There is some Domino configuration required, mostly to set up as an authorized DB2 user account.
The Notes database(s) that you want to integrate with DB2 must be created as DB2-enabled. If you have an existing database that you want to convert, you can make a copy or replica copy and mark it as a DB2 database. (It is not possible to convert existing databases simply through your new server configuration, or through a server-console command.) In your Notes database, you can then create a DB2 Access View (DAV), which sets up the appropriate tables in the DB2 storage. Note that you may have to clean your data to avoid data-type conflicts. Also note that these will add to the size of your storage needs, but will not...