How external transactions are handled in Activiti. If there is any ongoing EJB transaction then will Activiti transaction participate in that. I know that Activiti has their own transaction management,if something fails in my transaction then will Activiti rollback it's transaction.
If you configure the Activiti Engine with your own JTA transaction manager (like described in the user guide) you can have it participate in an EJB transaction. So then, when your transaction fails, the Activiti transaction will be rolled back as well.