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Browse Prior Art Database

Subset File Organization Method

IP.com Disclosure Number: IPCOM000084533D
Original Publication Date: 1975-Nov-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Lee, KY: AUTHOR

Abstract

An organization method for subset files is designed to be run under an Operating System with a direct access facility, such as a basic direct access memory (BDAM) with a direct access device. This method makes it possible to retrieve a subset from a file directly. No scanning is needed Operating System with a direct access facility, such as a basic direct access memory (BDAM) with a direct access device. This method makes it possible to retrieve a subset from a file directly. No scanning is needed in finding the members of a subset. This results in an improvement in run time as compared with conventional methods of using BDAM.

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Subset File Organization Method

An organization method for subset files is designed to be run under an Operating System with a direct access facility, such as a basic direct access memory (BDAM) with a direct access device. This method makes it possible to retrieve a subset from a file directly. No scanning is needed Operating System with a direct access facility, such as a basic direct access memory (BDAM) with a direct access device. This method makes it possible to retrieve a subset from a file directly. No scanning is needed in finding the members of a subset. This results in an improvement in run time as compared with conventional methods of using BDAM.

The speed is realized via illumination of unnecessary I/O operations during a job run. Paging for a subset from a remote TP terminal becomes possible. The direction of paging may be made forward or backward as desired, and it may be reversed at any point during the paging process.

The method includes establishing an index matrix in a BDAM data set, setup of a two-dimensional matrix to keep track of necessary attributes of the subsets in a file and their member counts. Each row of the index matrix contains the following: Subset identification. Current count of its members. Beginning address of a subset. Ending address of a subset.

Since the read write operation is accomplished one block at a time, the minimum size is one block long. A number of blocks may be preallocated for use in storing the index matrix, if the number of subsets is expec...