ACRONIS BACKUP AND RECOVERY 10 ADVANCED SERVER VIRTUAL EDITION - UPDATE 3 User Manual page 43

There is a certain risk that all but one backup will be deleted if the maximum archive size is set
improperly (too small) or a regular backup turns out to be too large. To protect the recent backups
from deletion, select the Never delete backups younger than check box and specify the maximum
age of backups that must be retained. The diagram below illustrates the resulting rule.
Combination of rules 1 and 2
You can limit both the backups' lifetime and the archive size. The diagram below illustrates the
resulting rule.
Example
Delete backups older than = 3 Months
Keep the archive size within = 200GB
Never delete backups younger than = 10 Days

Every time the retention rules are applied, the program will delete all backups created more than
3 months (or more exactly, 90 days) ago.

If after the deletion the archive size is more than 200GB, and the oldest backup is older than 10
days, the program will delete that backup.
 Then, if necessary, the next old backup will be deleted, until the archive size decreases to the
preset limit or the oldest backup age reaches 10 days.
Deleting backups with dependencies
Both retention rules presume deleting some backups while retaining the others. What if the archive
contains incremental and differential backups that depend on each other and on the full backups
they are based on? You cannot, say, delete an outdated full backup and keep its incremental
"children".
When deletion of a backup affects other backups, one of the following rules is applied:

Retain the backup until all dependent backups become subject to deletion
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