What is the best way to deal with a situation where the application is using an extended persistent context but yet there are several writes by an external process?

When a transaction completes the documentation says that an extended persistent context becomes detached from the db and reattached during the next unit of work.

When the persistent context is reattached a merge occurs on all elements in the extended persistent context does it not?

What happens if you are using an L2 cache?

Since Hibernate has no way of knowing if an external source has updated the database what is the best way to deal with maintaining data integrity?

I'm not sure of any way of really dealing with this scenario without select for update but doing so across a long running conversation will not do.

Optimistic locking is not possible since the schema is defined and there is no way to add a column for versioning

Any advice?

Thanks

You still can do optimistic locking by comparing all columns.

On the other points ... no idea, but I'curious as well :-)