Browse Prior Art Database

Selective Journaling

IP.com Disclosure Number: IPCOM000083513D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Hoff, CE: AUTHOR [+2]

Abstract

In mass memory systems employing a plurality of independent storage modules, for example, semiconductive memory modules, bubble memory units, direct access storage device (DASD) units, magnetic tapes, and the like, there is a small but finite probability that that unit will fail. Such unit failure can result in a host CPU associated with the mass storage system to abort the processing associated with data stored in such a failing module.

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Selective Journaling

In mass memory systems employing a plurality of independent storage modules, for example, semiconductive memory modules, bubble memory units, direct access storage device (DASD) units, magnetic tapes, and the like, there is a small but finite probability that that unit will fail. Such unit failure can result in a host CPU associated with the mass storage system to abort the processing associated with data stored in such a failing module.

One solution is to duplicate all data in the mass storage system. Such duplication results in unnecessary expense. Accordingly, critical data volumes (data addressable by a single name or number) are defined and identified for duplication using journaling techniques. Critical volumes in a preferred sense include that data necessary for continuous operation of a computer installation and its environs. Such definition does not alter the internal structural features of the data content; all control information associated with identifying and handling such critical volumes is performed by the host processor and the mass storage system, independent of user data structures.

The journal format contains the critical data volumes, plus associated control information pointing to target areas for the critical volume. In one system architecture, this could be a channel control word (CCW) or unit control block and the like, wherein an operating system can associate data volumes with location of such data volumes in a logical sense.

The logical allocation of journaling space can be device dependent, but transparent to the user. For example, if journaling is done on DASD, each track could have a space reserved for control information and the remainder usable for the critical volume. Such packing may be inefficient; i.e., the extent of the critical volume may be substantially less than the extent available in each DASD track.

In such instances, the data may be conca...