I'm not sure I understand your question. It depends on who initiates the transaction and what the transaction setting is for the bean. Skipping over the details, you can set up your bean to initiate its own transaction, be included in caller's transaction, or ignore any context transaction. Absolutely the very best explanation I have ever seen about this complicated subject is in the chapter on transactions in the free QuickStart Guide. The latest draft 4 of the guide can be gotten here:
I am sorry. I will try to be more precise.
I have 2 applications:
Session bean1. Transaction att: Required
Session bean2. Transaction att: Supported or Required.
What happens with the transaction when bean1 calls bean2?. Dos transaction work across applications? Will bean2 be running in the transaction bean1 started?
There are some pretty pictures in the quick start guide.