The default FORK handler in jbpm creates concurrent execution paths for every transition defined in the process flow (in FORK node). However, they are not executed parallel fashion.
Is it possible to write custom fork handlers, which starts separate thread for running every FORK-JOIN branch. This might allow true concurrent execution various branches in FORK.
The default jBPM fork handler doensn't implement 'real' concurrency, but it does implement 'business concurrency' (ie from a business point of view it is concurrent).
You could write your own fork/join implementation ... but I'm seeing a lot of Hibernate optimistic locking/stale object/... exceptions happening. Another problem is that the threads are not long-lived (ie when the DB/server crashes), and you need to recreate, restart and bring them back to the previous state. This all seems quite cumbersome, taking in account that the default fork overhead is minimal...