Browse Prior Art Database

Rapid Access Method for Fixed Block DASD Records

IP.com Disclosure Number: IPCOM000089156D
Original Publication Date: 1977-Sep-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Baird, R: AUTHOR

Abstract

A method for accessing records stored on a DASD (direct-access storage device) in uniform fixed block format, said DASD being responsive to channel command words and further the search arguments of said channel command words referencing variable length records in count key data format. The method comprises the steps of: 1) forming a single level null index of record references, and replicating the index a predetermined number of times on one or more tracks the record location in the DASD being derived from the reference: 2) inserting references into the index or indices responsive to channel programs at the time the data is created; and 3) accessing the index or indices responsive to each channel command word search argument in order to ascertain the record location.

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Rapid Access Method for Fixed Block DASD Records

A method for accessing records stored on a DASD (direct-access storage device) in uniform fixed block format, said DASD being responsive to channel command words and further the search arguments of said channel command words referencing variable length records in count key data format. The method comprises the steps of: 1) forming a single level null index of record references, and replicating the index a predetermined number of times on one

or more tracks the record location in the DASD being derived

from the reference: 2) inserting references into the index or indices responsive to channel programs at the time the data is created; and 3) accessing the index or indices responsive to each channel command word search argument in order to ascertain the record

location.

It is recognized that one of the reasons for a large inter-record gap between records on a disk is for the purpose of permitting an associated device control unit to calculate the location of the record from the search argument. However, according to the method, an index record may be formed which references each physical record on a track. The index record as shown, for example, in the figure is recorded several times around the track. The index record should not be program-addressable and the space to contain it must be deducted from the track data length capacity. Each entry into the index record contains control bits and the count. When a seek occurs, the first in...