In both the Source- and the Target Engine, if a flag is handled with a System- or User Event with severity Reject Root/Child, the item in question will be rejected. This means that the item will not flow on to the next step in the Migration process (a Reject severity in the Source Engine means that the item will not be available for the Target Engine and a Reject severity in the Target Engine means that the item will not be delivered to the Target System).
However, regardless of reject state, in both engines the processing of the item normally continues to end anyway. This is to get all possible events from the processing in order to be able to handle and correct more events at once. But sometimes a situation is so severe that continued processing of the item does not make sense and only creates a swarm of derived events that clutter up the Tracker and the picture in general. In these cases you can abort the processing of an item in response to a given flag.
This can be achieved by checking the Abort checkbox for the flag indicating that further processing of the item should be aborted if this flag is raised.
The Abort checkbox is only available if the Action is different from Ignore and the Severity is either Reject Root or Reject Child.
If Abort is checked for a given flag, this will show up as an exclamation point (!) in the Events column of the parent list:
Searching for the term 'abort' will find all occurrences of flags with check in Abort