multiple databases in a single RAC cluster

Hi, As much as Ive been browsing / studying rac... Im looking for a definitive answers about how many "databases" can be on one rac cluster.

Say I want to have 4 independent databases on one cluster, is that possible? I understand one can easily have multiple instances pointing to a single database (sga, control_file, db_name, spfile, archive_dest, etc) but what about several independent databses?

Any documents referencing this?

I found this on ask tom... just wanted to confirm with this group, probably in a more concise manner.
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:529123700346381713

So, How many databases (sga, control_file, db_name, spfile, archive_dest, etc) can be in a single rac cluster?

thanks

Bob

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