A rewritable data storage medium has a rewritable recording layer provided with a tracking structure. The recording layer has a data recording area. An erasable identification mark is present in an identification mark area other than the data recording area. The data recording area has a first tracking structure, whereas the identification mark area is substantially free from a tracking structure or has a second tracking structure substantially different from the first tracking structure, such as including concentric or interrupted spiral grooves. Thus erasure of the identification mark is practically impossible, because the location of the erasing spot of a recorder cannot be controlled precisely in radial direction in the identification mark area.