Are you talking about the RCU database, or the database where the data being reporting through OBIEE resides?
I don't think TimesTen is supported as an RCU platform. To migrate the RCU across databases I'm pretty sure you'd be looking at a reinstall/migration process.
If it's simply the reporting data then you make sure the database type is set correctly on the Physical DB object in the RPD, update the DSN, and assuming your schemas/tables/columns match *exactly* you should be good to go. I'd still want to check over data types etc though of the individual columns.
Nope, TT isn't supported for RCU...