When you use DUPOUT= the duplicate observations (whether you use NODUPS or NODUPKEY) are sent to the SAS member specified on the DUPOUT= parameter value, as shown below. If you have having difficulty, suggest sharing SAS log information for an accurate response. Also, consider that your BY variable list must be granular, to result in duplicate observations being adjacent in the sorted file, otherwise duplicates may not be removed as you might expect.
Scott Barry
SBBWorks, Inc.
Suggested Google advanced search argument, this topic/post:
proc sort dupout site:sas.com
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1 proc sort nodupkey data=sashelp.class out=class dupout=class_dup;
2 by sex;
3 run;
NOTE: There were 19 observations read from the data set SASHELP.CLASS.
NOTE: 17 observations with duplicate key values were deleted.
NOTE: The data set WORK.CLASS has 2 observations and 5 variables.
NOTE: The data set WORK.CLASS_DUP has 17 observations and 5 variables.
NOTE: PROCEDURE SORT used (Total process time):
real time 0.31 seconds
cpu time 0.04 seconds