galaxy flyer, one would discontinue the IAP at the minimum for circle to land (MDA) in case the visual cues aren't acquired as much as circle to land will be discontinued and MA for the IAP in use executed should the visual reference become insufficient. To picture it, let's say ILS 27 is IAP and the conditions aren't suitable to land on 27 but for 09. 09 doesn't have a IAP thus you will fly ILS 27 to circling minima MDA and circle to land on the 09. In case you decided to discontinue the circle to land you'll have to fly MA for the ILS 27.
Cheers.
