OpenJPA Slice addresses the same aspects that other providers address in their own way (Hibernate calls it Shards, do not know about EclipseLink equivalent). In future, JPA specification will standardize the behavior against multiple databases. It is necessitated by the interest in multi-tenancy as the applications move into cloud computing environment.
Hence, your effort investment in Slice (or some of its equivalent) would not go waste. The important architectural concern is two separate persistent contexts (i.e. EntityManager instances em1 and em2) connected to two separate database instances has a fundamental limitation. One of the core premise of JPA is that a persistence context forms a 'group' (in a mathematical sense of the word) i.e. the entities of em1 *can not* refer to entities in em2. Whereas, when an application is connected to multiple databases, at some point or other, a requirement will arise that would require instances from different databases to refer to each other. At that point, a solution has to be considered that can bring entities from multiple databases into the *same* persistent context. Slice does that today, so does Hibernate Shards. ----- Pinaki -- View this message in context: http://openjpa.208410.n2.nabble.com/How-to-find-entity-belong-which-EntityManger-tp6470903p6471780.html Sent from the OpenJPA Users mailing list archive at Nabble.com.
