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Modifications to a Storage Control Unit to Permit General Purpose Data Record Keys

IP.com Disclosure Number: IPCOM000084125D
Original Publication Date: 1975-Sep-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 4 page(s) / 39K

Publishing Venue

IBM

Related People

Aldred, BK: AUTHOR

Abstract

Storage facilities such as the IBM 3830 storage control and the IBM 3330 disk storage, support the random retrieval of data records by provision of a key area. When used, this contains the primary identification of the data portion of the record. Hardware identification of the appropriate record to be retrieved is supported by the provision of three channel commands, i.e.: 1. Search key equal. 2. Search key high. 3. Search key equal or high.

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Modifications to a Storage Control Unit to Permit General Purpose Data Record Keys

Storage facilities such as the IBM 3830 storage control and the IBM 3330 disk storage, support the random retrieval of data records by provision of a key area. When used, this contains the primary identification of the data portion of the record. Hardware identification of the appropriate record to be retrieved is supported by the provision of three channel commands, i.e.: 1. Search key equal. 2. Search key high. 3. Search key equal or high.

These commands assume that for efficient data retrieval, records will be organized in ascending key sequence across each track (and if using the multitrack capability of storage control, than across the tracks in order comprising a cylinder). This provision depends upon two assumptions: A. It is possible to arrange keys in an ascending order and that this reflects some useful organization of the data records. B. The identity of the relevant records is determined by a simple "equality" or "greater than" condition between the key data portion of the record and a comparison argument.

If this does not apply, it is necessary to retrieve data records by identifier (i.e., CCHHR) and allow the problem program, or the operating system access routines, to inspect the data record contents and determine the acceptability of the record.

Situations where existing provision is inappropriate include the following:

1. Multipurpose keys, e.g., an employee key containing the information sex, trade, department. In this example, it may be desired on one occasion to retrieve data on all males in a specified department, on another all plumbers, on another all female machine attendants. Any arrangement of information within the key can only cause the members of one class to collate together, e.g., all females, or all trades of the same type or all employees of the same department.

2. Keys which bear a more subtle relationship to the comparison argument than simple equality with/greater than the first n bytes, e.g., the use of a Cartesian coordinate reference as a geographic key associated with property information. In this example, the retrieval of data records may be such as to require all information pertaining to a certain area, i.e., a point-in-polygon condition needs to be determined.

Described are simple extensions to existing devices compatible with present functions and the addressing situation 1 above.

The maximum length of the key area on the data records of the IBM 3330 disk storage device is 255 bytes. This may be used to store one primary identification of the data record, but, for the reasons given above it would be extremely useful to enable it to store a number of identifiers. This is provided by a capability whereby the key area is viewed by the storage control unit under a program supplied mask; each bit in the mask indicates whether the corresponding byte of the key area should be considered. Thus for a key length

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