How to access Multiple DB2 Relational Databases In A Single Query
One way you can achieve this is via federation. In short words, if you want to access db_b from db_a, you catalog db_b in instance of db_a. You then create nicknames in db_a for the tables in db_b that you want to access. The nicknames can with some restrictions be treated as tables, so you can join a table in db_a with a table in db_b.