What exactly do you mean, three identical databases? If you really need to mirror databases, that may be something to do at the database server software level, not within EJB.
Sorry, bad wording. Three databases structured in exactly the same way but holding different information.
What I would like to do is use one set of components (Facade/EJB/Entity) to access each of the three depending on dynamic configuration. So I'm thinking that I either need to deploy 3 instances of these components under different jndi names? or is there some other way of doing this that i don't know about?