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Concurrent File Synchronization

IP.com Disclosure Number: IPCOM000050162D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Griscom, RE: AUTHOR

Abstract

Duplication of logic units is a state of the art technique for g improving availability. In order to work, however, the units must be initialized to the same state, or synchronized. This generally involves complex circuitry in addition to the normal functions. This invention describes a method for synchronizing any two direct access files, without assuming any additional circuitry. It also permits the using system to operate with one file until the synchronization is complete. The three steps of the process are as follows: 1. Initialization - A control bit indicates that the files are not synchronized. One of the files will be declared the primary file, and the other one the secondary file. The system will direct all writes to both files. It will direct all reads to the primary file.

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Concurrent File Synchronization

Duplication of logic units is a state of the art technique for g improving availability. In order to work, however, the units must be initialized to the same state, or synchronized. This generally involves complex circuitry in addition to the normal functions. This invention describes a method for synchronizing any two direct access files, without assuming any additional circuitry.

It also permits the using system to operate with one file until the synchronization is complete. The three steps of the process are as follows: 1. Initialization - A control bit indicates that the files

are not synchronized. One of the files will be declared

the primary file, and the other one the secondary file.

The system will direct all writes to both files. It will

direct all reads to the primary file.

2. Synchronization - Copy all data from the primary file to

the secondary file. This uses normal system resources and

is concurrent with other operations. However, each copy

operation (read primary, followed by write secondary) must

be completely executed so that no updates occur between

the read and the write.

3. Completion - Set the synchronization control bit. Both

files now contain the data that was originally on the

primary file, plus any updates made during normal

processing. The files are synchronized, and reads may be

directed to either file.

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