Executing EPP commands will normaly not result in any pending actions. However, the Registry may initiate certain actions that will trigger a message to be sent to the registrar, and all registrars are expected to regularly <poll/> all their messages to stay updated. The Registry automatically deletes messages that have not been retrieved within 30 days of their creation.
Please note that only the first message in the queue can be polled with EPP. This means that polling can only be performed by a single thread, and all messages must be acknowledged.