This is one of the obstacle which I was faced in my last assignment where I was supposed to make a universe by using tables from two different Databases.As we all know in Business Objects Release 3.1.One Universe is equals to One Connection i.e. one can use only one connection to make a universe.My project demanded to use two databases for designing one Universe which was very hard for me.
I contacted DBA team to create Db Links, so that I will be able to access the tables of one Database in the other database(which was the one containing the original Tables).For the same purpose we need to create Synonyms for the tables which needs to be accessed and then grants needs to be given in order to specify the desired schema which we want can access the Db Link and the tables of the Database.The Db Links were created due to which I was able to access the tables of the another Database.
A connection of the database was created in the Universe from which the Fact Tables and and other useful tables were to be used and for the other dimensions tables which were in some other Database.
Derived Tables were created for calling the tables from other Database along with the table name and the Db Link name.In the select clause we can use the columns which we will need in order to build the object so that their is no unnecessary load in the Universe.