AuthBy DBFILE authenticates users from a user database stored in a DBM
               file in the standard Merit DBM format. It is implemented in
               
AuthDBFILE.pm. It does not log (but does reply to)
               accounting requests. For more information about file formats, see 
Section 9.3. DBM user database. DBM
               files can be built from flat file user databases with the
               
builddbm utility. For more information about
               
builddbm, see 
Section 6.2. builddbm.
AuthBy DBFILE opens and reads the user database for every
               authentication. This means that if you change the user database DBM file,
               it will have an immediate effect. The DBM file is not locked when it is
               accessed.
            When attempting to authenticate a user, AuthBy DBFILE will first
               compare all the check items associated with the user in the same way as
               <AuthBy FILE>. For more information, see 
Section 3.35. <AuthBy FILE>. If all those match the
               attributes in the Access-Request message, AuthBy DBFILE will reply with an
               Access-Accept message containing all the attributes given as reply
               attributes in the user database. If the user does not appear in the
               database, or if any check attribute does not match, an Access-Reject
               message is sent to the client.