Is "Process scoped identity" the same thing as TopLink shared cache?

Bumped into this thread on my investigation of ORM solutions:
http://forum.hibernate.org/viewtopic.php?t=939623&highlight=toplink
What I would like to know is whether "Process scoped identity" as Gavin King puts it, is the same as TopLink shared cache and if so, whether this could cause deadlocks?
Quote:
    All the docs for Hibernate assume that you are working in a multi-user system,
    where process scoped identity is an absolute no-no - you would require
    synchronization on entity instances, which is guaranteed to result in deadlocks,
    since there is no possible "natural" order in which to obtain locks.

Yes, process scoped identity is basically what TopLink's shared server session cache is offering. Having shared instances is a huge benefit for performance and is most noticeable with read-only and read-mostly data types shared across users.
Yes, we do need to have locking to ensure that changes are safely written into the shared instance and that transactionally isolated (UnitOfWork) copies are safely made in a row consistent fashion. Although I cannot comment on Hibernate's implementation I assume that whatever object type they use in their shared (L2) cache offers the same concurrency protection to ensure that users get consistent data and that concurrent writes do not corrupt the cached object structure.
I guess the only real difference is the object type cached. TopLink cached your business object and Hibernate caches a custom object representing the state of you object. Both need to ensure proper locking for concurrency protection but TopLink does not need to rebuild an instance for each client session unless wanted/needed.
Doug

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