Yes, MLOAD supports the insertion of deuplicate records and this is the main difference between the FASTLOAD and MULTILOAD.
The below thread should give you more details...
As Multiload handles duplicates then if have update statement and finds multiples rows to update then multiload updates which row?.
NOPI tables are inherently MULTISET, and because the row distribution is not based on any index they so it is possible that they can reside on a different AMP so duplicate row checking is not possible. So when the FastLoad targets a a NOPI table, no check is made for duplicate rows and are not discarded!
Thanks Qaisar... Now i got that Fload will insert duplicate rows in NOPI tables. How does it handle that when there is some interuption and after that the Fload is restarted?