With so many Hibernate specific settings I'd think you would want to try a hibernate specific forum, or at least try using TopLink/EclipseLink before posting in a TopLink product forum.
That said, where and why are you getting the exception? If you are just merging or persisting a Topic entity into PU_A, it shouldn't matter that Topic references a detached IntegrationDepartment (any IntegrationDepartment instance read in through PU_B is detached from the PU_A perspective). I can only see this exception occurring if you are using getReference somehow and the entity gets removed or deleted. If that is the case, you might ensure it is fully loaded from PU_B and then detached before associating it to PU_A.
Thank you very much for your consideration. Yes it does matter, because after entityManager which driven by PU_A merge the Topic entity, it returns the refreshed version of Topic. But at that point it can not load the IntegrationDepartment topic cause of its mananagement of this entity belonged to another entityManager which driven by PU_B. even if you would be right about detached mentioning, as i understood that i should manual load IntegrationDepartment entiy by PU_BEntityManager just after PU_AEntityManager merge process. That means a manual interception and requires control every process because how can i know an entity that will be merged, has if any entity referenced exists which by driven foreign entityManager?
Sorry for my poor english and hope that you understand.
Not quite what I meant - I was suggesting you load the entity immediately after reading it from PU_B, or anytime before associating it into PU_A, so before the merge. What you have not shown though is any code on how you are obtaining IntegrationDepartment and integrating it into PU_A, or what you mean by it is returning a refreshed version of Topic. This problem could also be the result of how your provider works internally - this is a TopLink/EclipseLink forum post so I cannot really tell you why you get the exception other than it would be expected to work as described with EclipseLink as the JPA provider.
So the best suggestions I can come up with are prefetch your entity, try posting in a hibernate forum, or try using EclipseLink/TopLink so someone here might be better able to help you with any problems that arise.