Progressive incremental backups

The terms differential and incremental are often used to describe backups. The standard method of backup used by Tivoli® Storage Manager is progressive incremental.

The terms differential and incremental have the following meanings:

A differential backup backs up files that have changed since the last full backup.
- If a file changes after the full backup, the changed file is backed up again by every subsequent differential backup.
- All files are backed up at the next full backup.
An incremental backup backs up only files that have changed since the last backup, whether that backup was a full backup or another incremental backup.
- If a file changes after the full backup, the changed file is backed up only by the next incremental backup, not by all subsequent incremental backups.
- If a file has not changed since the last backup, the file is not backed up.

Tivoli Storage Manager takes incremental backup one step further. After the initial full backup of a client, no additional full backups are necessary because the server keeps track of when files need to be backed up. Only files that change are backed up, and then entire files are backed up, so that the server does not need to reference base versions of the files. This means savings in resources, including the network and storage.

If you choose, you can force full backup by using the selective backup function of a client in addition to the incremental backup function. You can also choose to use adaptive subfile backup, in which the server stores the base file (the complete initial backup of the file) and subsequent subfiles (the changed parts) that depend on the base file.