Browse Prior Art Database

Backup Utility Shadow Table

IP.com Disclosure Number: IPCOM000035132D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Buquoi, GH: AUTHOR [+3]

Abstract

A method is described which guarantees that the Backup Database Table always reflects the correct data about the latest Backup.

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This is the abbreviated version, containing approximately 53% of the total text.

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Backup Utility Shadow Table

A method is described which guarantees that the Backup Database Table always reflects the correct data about the latest Backup.

The Backup Utility creates a table in the user's database. In this table it stores information about each OS/2 file that it finds in the database directory. When the utility runs with the 'changes only' option, it uses the information stored in this table to determine which database files have changed since the last Backup was run.

At the time Backup runs, the database log file may be quite large. The Backup Utility itself causes the log file to grow due to all the table updates it performs. The log file is backed up with the rest of the database files. If it is left this large, it may take one or two diskettes to hold just the backed up log. So, Backup truncates the log before calling the OS/2 Backup Utility.

At this point the database table created by Backup contains all the information about the files that are being backed up. These updates to the table are not yet commited, they are still in the log. Backup does not want to commit the updates until after the Backup is complete. If it does and the OS/2 Backup fails, the table will reflect data about a Backup that did not take place. If Backup does not commit the updates, they will be lost when the log is truncated and it will be unable to commit after the OS/2 Backup completes. In this case the table will either not exist or contain data about the last previous backup instead of this one.

Th...