How to change data source of Universe

Hi,

I have two databases called A_Database and B_Database

Same tables and data are in both the databases.

I created universe U_universe using A_Database. It is working fine

Now I would like to change from A_Database to B_Database in U_universe without affecting any thing in U_universe because tables and data are same.

Please let me know following doubts.

1.How to do above things?

2.if A_Database and B_Database are in different server, how to overwrite data source in the universe

3.if A_Database and B_Database are in the same server, how to overwrite data source in the universe

Thanks and Regards,

Manjunath