This International Standard specifies the mechanical, physical, and optical characteristics of a 130 mm optical disk cartridge (ODC) that employs thermo-optical Phase Change effects to enable data interchange between such disks. This International Standard specifies two types: - Type RW (Rewritable) provides for data to be written read and erased many times over the recording surfaces of the disk. - Type WORM (Write Once Read Many) provides for data once written to be read a multiplicity of times. This type uses a Write Once Read Many times recording material (written marks cannot be erased and attempted modifications of the written marks are detectable). Multisession (incremental write operations) recording may be performed on Type WORM disks. The disk is two-sided with a nominal capacity of 15,0 Gbytes per side and the cartridge (two sides) provides a nominal capacity of 30,0 Gbytes. This International Standard specifies: - the conditions for conformance testing and the Reference Drive; - the environments in which the cartridges are to be operated and stored; - the mechanical, physical and dimensional characteristics of the cartridge so as to provide mechanical interchangeability between data processing systems; - the format of the information on the disk, both embossed and user-written, including the physical disposition of the tracks and sectors, the error correction codes, the modulation methods used; - the characteristics of the embossed information on the disk; - the thermo-optical characteristics of the disk, enabling processing systems to write data onto the disk; and - the minimum quality of user-written data on the disk, enabling data processing systems to read data from the disk. This International Standard provides for interchange between optical disk drives. Together with a standard for volume and file structure, it provides for full data interchange between data processing systems.