What "Get delta only once option" in DTP do??.

Hi

I want to know What "Get delta only once option" in DTP do??. If my data source does not provide delta(only full update possible), and there are hard deletions in the source(with no reverse records or deletion indicators), will this option in DTP allow me to get the correct data in BW??

If this is possible then please let me know how to get it done with a small example. I need to know the sequence of data loads and settting in DTP and infopackages.