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Browse Prior Art Database

Generalized Record Format

IP.com Disclosure Number: IPCOM000076063D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Johnsen, RL: AUTHOR [+2]

Abstract

Described is a record format supporting data management requirements. Control intervals allow data to reside on a wide range of devices and to be stageable, both without modification, and allow context re-establishment over unrecoverable data and backspacing without indexing or chaining. Record control information is uncomplicated and records are largely self-describing and variable in length. Control Intervals.

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Generalized Record Format

Described is a record format supporting data management requirements. Control intervals allow data to reside on a wide range of devices and to be stageable, both without modification, and allow context re-establishment over unrecoverable data and backspacing without indexing or chaining. Record control information is uncomplicated and records are largely self-describing and variable in length. Control Intervals.

Under the control interval concept, the byte space is logically segmented into blocks each containing an equal number of bytes. At each control interval boundary, up to and including the last control interval in which stored records are recorded, record control information will be recorded. It is required that each control interval boundary coincide with the start of a record or record segment. Fig. 1 shows a byte space divided into control intervals of 800 bytes. For comparison purposes, Fig. 2 shows variable length records in a byte space with no control intervals, while Fig. 3 shows the same records mapped onto a byte space using an available space method of orienting records to control interval boundaries. In particular, RC(x) describes an available space record of 200 bytes. Fig. 4 illustrates the records described in Fig. 2 mapped onto a byte space described in Fig. 1, utilizing a segmented record method of orienting records to control interval boundaries. RC(3)(A) and RC(3)(B) describe the two parts of a 500 byte record segmented into 200 and 300 byte segments.

The choice between methods described in Figs. 3 and 4 can be made based on the amount of available space generated, user option, availability of a space reclamation facility, or record size, among others. In addition, control interval size may be judiciously chosen to minimize (or in the fixed length record case, eliminate) available space of record segments generated, due to control interval boundaries. Once the records have been mapped into the byte space, and oriented to control intervals appropriately, the data may be arbitrarily broken into physical blocks and extents, across devices if required, without further modification or addition of any other control information. Staging and reblocking can occur without either inspection or modification of the data and recovery, context re-establishment, and backspacing may be accomplished on a control interval basis. Record Control Information.

Each stored record, or stored record segment, is preceded by record control information (RC) mentioned above. In general, the first byte of each stored record or stored segment is a record control byte. Contained in this byte is information as to length of the record; whether the record contains live data or a deleted record (available space); whether the control interval contains a complete record or a segmented record, and the segment thereof; and whether control entries follow t...