Abstract: Disclosed is a system that stores write management information identifying which sectors have been written and which sectors are available to be written in a magneto-optical disk with write-once-read-many (WORM) capability. The write management information is stored in a separate write management directory on the media, which is typically loaded into the drive controller memory when the media is first loaded into the drive. Whenever the drive receives a write command, it checks the write management directory to determine if the sector has already been written. If the directory indicates that the sector has already been written, the drive returns an error, otherwise, the drive writes the sector and updates the write management directory. In the preferred embodiment, two separate methods are used to indicate that a sector has been written.

Abstract: Disclosed is an apparatus and method for defining magneto-optical disk media and an optical data storage device that allows the media to be convertible from writable to read-only. The media has a media descriptor table contained within a control track which is modified to define the media as a new media type. Previously manufactured drives will not recognize the media type, and therefore, will not read or write the media, so the data on the media is protected from being destroyed by such drives. The invention also defines a storage state bit within each sector of each track of the media, that defines whether the sector is writable or read-only. With this bit set into the writable state, the sector can be written many times. Once the bit is changed to read-only, however, the sector can no longer be written. The data storage device of the invention will not reset the bit, once it is set to the read-only state. The invention defines two locations for the storage state bit.