Hibernate and the Unit of Work pattern and session detaching

Question

Hibernate with the Unit of Work pattern is best suitable for HTTP solutions but my server has permanent connected users and it's efficient to keep all their data in the memory. With session-detached objects I can't use lazy loading and many hibernate features also expects me to use the Unit of Work pattern. Does Hibernate offer any good solutions to work with session-detached objects? Merge is not good enough here because it's the same redundant data loading (even from cache). Or should I use other solutions instead of hibernate for this kind of server? Any good ORMs?