"recover as a unit" and delta extractors

We are in the process of designing our job recovery and one thing that is a little unclear is what will happen with Delta queues when a job falls over.

If I have 3 delta dataflows in a workflow labelled as "recover as a unit" does this mean if the 3rd one fails, all 3 delta queues will reset back to before the job ran ?

What happens to destination tables ? Are the rolled back ? if my delta applies an insert when it is re-run that had already been applied, won't it just fail due to duplicates ?

Any recommendations / best practice in this area is appreciated.

Thanks,

Leigh.