goto any table containing these fields and look at check table...
goto se84->abap dictionary->fields and enter these field names.... u will get list of tables.... now goto se11 and enter any of these tables.... goto the required field and check if the check table column is filled....
else.. double click on the field... u will find check table name...
that means this field is primary key in that table(check table).
Regards
Vasu
