an optical archive storage system includes a large number of off - line optical disks which are selectively transported to read / write units by a robotic manipulator . access to the data files on the disks is maintained and controlled through the use of a token file on a magnetic storage device on a controller computer for each data file on each disk . the file attributes which the operating system of the computer assigns to the token file are used to control access and ownership of the data files on the disks .