if you are entering from a command line you need single quotes around it:
CALL PRGM1 (‘Inv’)
if you are entering the Inv in a screen field, the field needs to be defined to allow lowercase; otherwise it will convert the parameter
Adding to the above, consider whether the processed information has actually been shifted to upper case. When you render the information, ensure the rendering command or engine is capable of displaying both upper and lower case.
Or is that exactly the problem?