Format level identifier
The Record Format level identifier is a 13 byte string (looking like a hex string). Way back is was an arbitrary string created when the file was created, but today it calculated by a 'secret' formula consisting of field name and some of the attributes. If you have an old R1 s/30 file and a newly created file, the record format level might be different. The field text is NOT one of these, but the length and field order is. When you compile the DDS of the PHYSICAL file this value is calculated and stored as a part of the file. When you compile a logical with NO format changes (except keyfields, select/omit etc) the identifier is copied from the physical. When you compile an RPG program the identifier is copied from the file used. Note that a file also have a member level identifier and a file level identifier, but here we only talk about the record level identifier.
(by Henrik Krebs)