It is possible. Please read this article:
Basically, the models in ActiveJDBC find a connection on current thread, and operate on that connection. This means that if you place a connection on thread that points to one database, then read a model from it, close connection, then open a connection to a different database with the same schema, and save that same model, the second transaction will be sent to the second database. So long you have identical structure of related tables, it will work.
This interesting feature makes it easy to use ActiveJDBC to write data migration programs.
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