An optical data storage medium (1) is described. The medium (1) has an optically readable information layer with a first optical reflectivity. An annular zone (12), outside the user data recording area (2) has at least one first type (5) of sector provided with a permanent information mark (7), having a second optical reflectivity. The zone has at least one second type (6) of sector provided with a recordable identification mark (8), having a third optical reflectivity different from the first optical reflectivity. Thus, a hybrid bar code like structure, with both permanent and recordable information requiring little radial space, is provided. Further, methods to read such permanent information marks (7)/recordable identification marks (8) and to write such recordable identifications marks (8) are disclosed.