Please read the documentation.
Each AOLserver pool contains connection information, you can connect to multiple Oracle servers, or an Oracle server and a Postgres server, or Oracle/Solid/Sybase/MySQL/Postgres servers ...you can do whatever you want.
In your previous, redundant, thread Jeff makes clear that if you want to join across two Oracle db servers or otherwise integrate data at the Oracle level ... then AOLserver/OpenACS has absolutely nothing to do with it. You do it in AOLserver/OpenACS in exactly the same way you'd do it from SQL*Plus, which means you need to learn more about Oracle by reading their documentation and experimenting.
