proc datasets modify after copy

[proctice]

If you copy a data set to a different library then use the modify statement, does it modify the data set in the original library or in the library you copied to?

Also, can you use drop and keep statements or data set options in proc datasets?  Thank you.  

[Reeza · Accepted solution]

The lib option in the PROC DATASETS statement are the ones that is modified. If you don’t specify one, I think it’s the work library. 

Not sure about data set option but I suspect not.