I have also posted this question in SAS forum, but since your blog gets so much attention I thought it might be good to post it here as well. I get temp datasets 'sometimes' when using this feature:

NOTE: There were 456 observations read from the data set WORK.AVERAGE_LT700.
NOTE: There were 480 observations read from the data set WORK.AVERAGE_LT700_PREP.
NOTE: There were 480 observations read from the data set WORK.AVERAGE_LT700_PREP_TWO.
NOTE: There were 456 observations read from the data set WORK.AVERAGE_700_800.
NOTE: There were 480 observations read from the data set WORK.AVERAGE_700_800_PREP.
NOTE: There were 480 observations read from the data set WORK.AVERAGE_700_800_PREP_TWO.

If I don't delete the prep and prep_two my data set grows in triplicate. Can you help me understand why this is happening?

Thank You,
Mark