ONGSOURCE
ONGSOURCE returns a graphic string containing the DBCS character that caused the CONVERSION condition to be raised.
It is in context in an ON-unit (or any of its dynamic descendants)
for the CONVERSION condition or for the ERROR or FINISH condition
raised as the implicit action for a CONVERSION condition.
If the ONGSOURCE built-in function is used out of context, a null GRAPHIC string is returned.
