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Description of Full, Incremental, and Differential Backups
Article ID: 136621 - View products that this article applies to.
This article was previously published under Q136621
This article describes full, incremental, and differential backups. The Backup tool in Windows 95 supports full and incremental backups. Differential backups are not supported.
Backup uses backup file sets to help you manage backing up drives, folders, or files. Incremental and differential backups rely on an initial full backup of the drives, folders, or files in question.
Many Windows 3.1-based backup programs use the archive bit to mark files that have been backed up. Backup does not use the archive bit in any way. The decision as to whether or not a file should be backed up in an incremental backup is based on the filename, its last modified date, and the date of the last incremental backup, all of which are stored in the file set.
Full Backup (or Reference Backup)When you set the Backup Type setting to Full, all the files and folders on the drive are backed up every time you use that file set. To set the backup type, click Options on the Settings menu, and then click the Backup tab.
Incremental BackupAn incremental backup provides a backup of files that have changed or are new since the last incremental backup. To start the process, a file set with the incremental option selected is used to perform a backup. You can select the backup type by clicking Options on the Settings menu, and then clicking the Backup tab.
For the first incremental backup, all files in the file set are backed up (just as in a full backup). If you use the same file set to perform a incremental backup later, only the files that have changed are backed up. If you use the same file set for a third backup, only the files that have changed since the second backup are backed up, and so on.
In Backup, you can select files and/or folders to be backed up. If you select a folder, all the files and folders within that folder are selected. In an incremental backup, if you select a folder, files that are added to the folder are included during the next backup. If you select specific files, files that are added to the folder are not included during the next backup.
To reset a file set so that the next backup backs up all files, and not just files that are new or have changed, follow these steps:
Monday - Perform the first incremental backup of selected files and/or folders using a file set with the Incremental option enabled. Tuesday - Perform another backup with the backup file set you created Monday. Only files that have changed since Monday's backup are backed up. Wednesday - Perform another backup with the backup file set you created Monday. Only files that have changed since Tuesday's incremental backup are backed up.
Differential Backup (Not Supported in Backup)A differential backup provides a backup of files that have changed since a full backup was performed. A differential backup typically saves only the files that are different or new since the last full backup, but this can vary in different backup programs. Together, a full backup and a differential backup include all the files on your computer, changed and unchanged.
Monday - Perform a full backup and save the file set. Tuesday - Perform a differential backup using the same file set. All files that have changed since the full backup are backed up in the differential backup. Wednesday - Perform a differential backup using the same file set. All the files that have changed since Monday's full backup are backed up.