The present invention relates to a re-writable data storage member (10) comprising a plurality of spaced apart addressable data storage areas (12) for recording and storing data and a plurality of non-data storage areas (15) interposed between adjacent ones of the addressable data storage areas for recording signals not representing data, the storage member being adapted to be scanned in a direction over the storage areas. According to the invention the storage member is characterised in that one of the addressable data storage areas contains first machine readable indicia indicating that the storage member contains data which is not to be changed from any original recording of the data, another of the addressable data storage areas contains second machine readable indicia indicating whether or not the storage member has been erased of data in its entirety, and each of the non-data storage areas contains third machine readable indicia indicating whether or not one of the respective adjacent addressable data storage areas can be written into. The invention also relates to a data storage system comprising a re-writable data storage member as above and to a method of operating such a data storage system.