Multithreaded access to TopLink API

Question

Hi,
If several threads need to access the TopLink API for a given Project, what can be shared and what can't be shared or must be synchronized? Should a different DatabaseSession be used for each thread?

Answer 1

I agree with the previous answer. Using server sessions will provide the benefit of a shared cache for all clients.
On the other hand, if I am ready to give up this benefit, can I use DatabeSession in a multi-threaded environment?There are other things that speak against this approach
I will definitely need to:
- ensure each thread uses its own database sessionWith a shared cache, you get repeatable reads at the object level. Since the shared cache maintains Object identity for ALL Threads, you don't have to worry about read-only Objects going stale as Transactions from other Threads are committed. Using Multiple DatabaseSessions, you'd have to consider some sort of OptimisticLocking for all Objects since many Threads could have "copies" of the same data in the database.
- synchronize accesses to the Project, for example when creating a new DatabaseSession for the client.
Is that engouh? Are there "hidden" shared resources between DatabaseSession instances that would compromize the approach?There are probably other "hidden" problems. One I can think of off hand is that TopLink also manages sequencing at the Session level. So more than one DatabaseSession would mean that each Session would not be able to cache sequence numbers (which would slow down inserts considerably).
Regards,
Thierry.