Just to clarify something stated above... This actually NEVER affects JPA. JPA says that resource-local transaction (EntityTransaction) are only valid in non-DataSource cases.

According to JPA all other cases must use JTA (BMT or CMT) to control txn boundaries and implicitly or explicitly join the EM to that txn.

Hibernate does allow DataSource in combination with resource-local transactions.

I went ahead and commited the proposed PR with some modifications - specifically logged warnings and warnings in the documentation about enabling this "for perf reasons" when the DataSource/connection-pool are not configured to disable auto-commit.