Why do programmers not learn DeMorgan's laws?
IF SQLCODE NOT EQUAL 100 OR 0
is a short form for
IF SQLCODE NOT EQUAL 100 OR SQLCODE NOT EQUAL 0
and if SQLCODE is 0 then it is not equal to 100 -- TRUE condition; if SQLCODE is 100 then it is not equal to 0 -- TRUE condition; if SQLCODE is anything else it is not equal to 100 and it is not equal to 0 -- TRUE condition. In other words, you're going to do the PERFORM / GOTO no matter what the value of SQLCODE is.
Note that this is a good example of why we on this forum want to see code -- your original post has a DISPLAY with no IF logic, and the IF statement you posted only has one condition (so DeMorgan's Laws don't apply).