Increase EFFICIENCY of a SAS code

THINK Before You Type. One of the best practices of a good programming is planning before you type. Try to keep the code as simple as possible. Use procedures more than datasteps. For 
example, permanently save only the final data set. Use temporary data sets to store intermediate results.

Instead of this:

data Mylib.New;
set Mylib.Sept Mylib.Oct;
programming statements
run; 
data Mylib.District;
set Mylib.All Mylib.New;
programming statements
run;

Use this:

data New;
set Mylib.Sept Mylib.Oct;
programming statements
run; 
data Mylib.District;
set Mylib.All New;
programming statements
run;