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Improved Save/Restore

IP.com Disclosure Number: IPCOM000041389D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 66K

Publishing Venue

IBM

Related People

Crowley, TR: AUTHOR [+3]

Abstract

The IBM System/38 has a virtual memory where the main storage and disk enclosure storage are treated as a single-level storage space. The system save and restore utilities take on a greater importance in a system of this type. A catastrophic failure of even a single disk enclosure could destroy or severely damage the system data and adversely affect the user's ability to resume normal use in a reasonable amount of time. In the past an auxiliary storage save/restore (ASR) program was used to save all of the data on the disk enclosures. The disk enclosures were read by sequential physical disk address and saved on tape. However, the relatively slow data transfer rate of tape becomes the restraining factor in the save operation.

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Improved Save/Restore

The IBM System/38 has a virtual memory where the main storage and disk enclosure storage are treated as a single-level storage space. The system save and restore utilities take on a greater importance in a system of this type. A catastrophic failure of even a single disk enclosure could destroy or severely damage the system data and adversely affect the user's ability to resume normal use in a reasonable amount of time. In the past an auxiliary storage save/restore (ASR) program was used to save all of the data on the disk enclosures. The disk enclosures were read by sequential physical disk address and saved on tape. However, the relatively slow data transfer rate of tape becomes the restraining factor in the save operation. For example, a System/38 configured with the maximum amount of auxiliary storage could require up to 19 hours to completely save the auxiliary storage data. By compressing the data and thus reducing the amount of data to be transferred to the save media, the amount of time required for the save operation is reduced. ASR implements compression of strings of zeros and blanks to reduce the amount of data to be written to the save media. However, even with the performance improvements realized from this technique, the save operation still lasts an inordinate amount of time. It is necessary to further reduce the amount of data to save. The present method improves performance of the save/restore operation by eliminating the transfer of deleted objects. An object is a named item that is stored on the system. Examples of objects are: programs, files, libraries, and queues. An object is composed of sectors on the disk enclosure. Each sector is composed of a header and of data and has an associated record number. The record number progresses from 0 (zero) to N, where N is the total number of sectors on the disk enclosure. When an object is created, the storage management component will determine the number of contiguous sectors required to contain the object. Storage management requires that this number of contiguous sectors always be a power of 2 in size (i.e., 2OE, 21, 22 . . .). In the sector header is a 4-bit field referred to as the extent size (Fig...