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 specific scenarios (Retention Rules) when online data should be 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. In the Choose a retention rule for this backup set screen, retain the default settings unless there are specific backup set retention requirements.
For more details on retention options, see the online help for the screen.
2. When you have made the needed selections, click Next.
F1 Help: "Set Properties - Retention tab"