If you talking about proc SORT it has only NODUPKEY option (to my knowlege), and this is a description:
checks for and eliminates observations with duplicate BY values. If you specify this option, then PROC SORT compares all BY values for each observation to the ones for the previous observation that is written to the output data set. If an exact match is found, then the observation is not written to the output data set.
Be careful with this. NODUPKEY will not remove duplicate records; it removes records with duplicate keys. The NODUP option gets closer, but it still assumes that you have sorted by a sufficient number of keys to uniquely identify the records.