Working with backup sets : File system backup sets (Windows) : Creating a File system backup set : Specifying a retention rule
 
Specifying a retention rule
The retention feature allows you to define retention rules, which are specific scenarios when data should be kept online, or otherwise deleted. Retention rules are applied per backup set, but are enforced only on demand or on schedule. For more information, see “Working with retention rules”.
1. On the Choose a retention rule for this backup set page, retain the default settings unless there are specific backup set retention requirements.
For more details on retention options, see the F1 help for the dialog box.
2. When you have made your selection, click Next.
F1 Help: "Set Properties - Retention tab"