Thanks for your suggestion, now I understand.
I don't think it will solve my problem, because with this solution I will have several independent programs (or threads, whatever) executing different code in the *same* *physical* instance of the EJB at the same time. To avoid that, I would have to add "synchronized ( ) { ... }" statements on every public business method, something which is strictly forbidden in JEE as I understand it?
I will have to re-think and redesign my solution. Too bad I did not anticipate resource/pool handling to be this bad.
Come to think of it, if database resource pooling is handled in the same manner, all the effort I have put into sizing my databases and database pools are really void. I have absolutely no guarantees whatsoever that my application servers will not decide to create more database connections than the database can handle / are sized to.
This is potentially a very big problem.
I think it is a bug.
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