Difference between CHAINing a file name & CHAINing a record name

Hi All,

I have always been chaining a file name (habit since long) but today I
found that when I chained using the file name the record was not found &
when used the same key & chained using the record name the record was
found. Why is this so ?? Which is correct ??

I'm sure this might already have been discussed before - if so can anyone
send me the link - Thanks.

Eg of not found:
chain (prbanb:'IN') inprxxl0;
if not %found(inprxxl0);
leavesr;
endif;


Record found:
chain (prbanb:'IN') inprxx5;
if not %found(inprxxl0);
leavesr;
endif;

Thanks & best regards
Ewart