Browse Prior Art Database

Space Management Method

IP.com Disclosure Number: IPCOM000078157D
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Chesarek, DJ: AUTHOR

Abstract

This is a space management method for disk file space allocation in a system in which the extent of space required to store a logical record is not known, at the time space must be allocated. Such is the case in a noncoded information system where the length of the logical record which represents a compressed image is unknown until after the original image has been compressed, which is also after space must be allocated to receive the record.

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Space Management Method

This is a space management method for disk file space allocation in a system in which the extent of space required to store a logical record is not known, at the time space must be allocated. Such is the case in a noncoded information system where the length of the logical record which represents a compressed image is unknown until after the original image has been compressed, which is also after space must be allocated to receive the record.

The space allocation algorithm of Figs. 1 and 2, will allocate space on a disk pack to store a compressed image of either known or unknown extent. Each pack contains a Volume Table of Contents (VTC) which describes the image space for that pack. The data management program space allocation algorithm maintains two lists for each pack: the "available" list identifies those cylinders having more than T units of free space, and the "used" list identifies those cylinders which have less than T units of free space.

When a request for space for a compressed NCI image of unknwn extent is presented to the Space Management algorithm of Fig. 1, it allocates space on the first cylinder in the space available list, stores the compressed image on the selected cylinder, and then decrements the available space buy the extent of the image just stored. If the space available still exceeds T units, the cylinder remains on the available list, otherwise it is transferred to the used list.

If the image does not fit the ava...