Abstract: A system and method for defining rewriteable data storage media defined by ECMA Standard ECMA-272 2nd edition (1999) for 120 mm DVD rewriteable disk (DVD-RAM) as a write once data storage media and for storing data thereon. The apparatus consists of a data storage device for reading and writing data on the media, the media, a media type indicator in the media, two write protect flags in the user data area of the media, and programming to examine the two write protect flags prior to a write, erase, or format operation. If both flags match and the media type indicator is write once, the drive is prevented from writing to the user data area if both flags are in the data written state. If both flags do not match after two re-reads, an error message is generated. If both flags are in the data unwritten state, data is written to the user data area and both flags are set to the data written state.

Abstract: A method for selectively enabling writing of data multiple times onto a write-once read-many optical disk by a host system, the disk having a disk type indicator, and each sector having a SWF field and a flag field and user data, wherein new data bits replace existing data bits in a one-for-one ratio without mapping, comprising the steps of: reading a disk type indicator; setting a firmware flag allowing writing to the disk if the disk type is erasable WORM; receiving a write command from the host system, the command specifying a sector to write to; reading the contents of the disk SWF and flag fields for the sector; overwriting all user data on the sector with all zeroes if the firmware flag is set; replacing every user data bit in the sector with a zero in a one-for-one ratio without mapping; and resetting the contents of the disk SWF and flag fields to indicate the sector is available for writing.