The argument to UW_acc should be an element of the set OBS. but you are passing OBS_BY, which is instead a subset of OBS. Same story for EP_incr and Time. What does your pat_opt function expect as input?
By the way, you can combine the READ DATA statements as follows:
read data work.pat_data into OBS=[_n_] pat_ID=pat_ID UW_acc=UW_pattern_acc EP_incr=EP_pattern_incr Time=Year;
... View more