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Space Reservation for Maximum Overlap Using a Mass Optical Storage Device

IP.com Disclosure Number: IPCOM000037290D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Freeman, HL: AUTHOR [+4]

Abstract

Long delays in optical device mount times are avoided by using a method of reserving space on optical media before it is mounted. This permits users writing objects on the media to continue before the media is mounted and the data are actually written. To reserve space, the method maintains a file on a direct access storage device (DASD) which keeps track of the available space for each optical disk and compares the size of each object to be written to the optical disk to the amount of space available.

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Space Reservation for Maximum Overlap Using a Mass Optical Storage Device

Long delays in optical device mount times are avoided by using a method of reserving space on optical media before it is mounted. This permits users writing objects on the media to continue before the media is mounted and the data are actually written. To reserve space, the method maintains a file on a direct access storage device (DASD) which keeps track of the available space for each optical disk and compares the size of each object to be written to the optical disk to the amount of space available.

When a new object is written to optical disk, it is staged into a DASD folder and written to optical disk when a close request is received from the application. It is possible that the optical disk is not mounted to an optical drive at this time. In order to avoid a 15- second (or longer) wait that is required to mount the optical disk, the amount of space used on the disk is kept in a system table on DASD. An entry is kept in this table for every volume in the mass optical storage device and every volume on the shelf. The amount of space available on a volume is compared against the size of the object. The size of the object is computable since the object was completely written to the DASD folder. If the object fits, then the application is allowed to continue. The mount of the optical disk and the transfer of data take place asynchronously.

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