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Browse Prior Art Database

Efficient Page-Fixing Method using a Control Block

IP.com Disclosure Number: IPCOM000037517D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Allan, AL: AUTHOR [+5]

Abstract

Disclosed is a method of minimizing needless fixing and unfixing of pages of records when sequentially scanning a database file.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 100% of the total text.

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Efficient Page-Fixing Method using a Control Block

Disclosed is a method of minimizing needless fixing and unfixing of pages of records when sequentially scanning a database file.

Records of a database are grouped into pages. A page is the unit of I/O for the file. The disclosed method provides for an effficient means of scanning the records in the file without the overhead of fixing the page in memory each time a record is accessed. Instead, one page is fixed in memory until all the records on it have been scanned.

When the database file scan is initialized, a cursor is established, marking the record position within the file.

A control block, existing for the duration of a cursor, contains the following information: a flag indicating whether the current page is fixed, and a flag indicating whether the current record is at the beginning, middle or end of the page.

Pages are unfixed when a new page is read, not for each new record. Specifically, a page is unfixed after reading the last physical record (when scanning forward) or first physical record (scanning backward).

Disclosed anonymously.

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