D-Link DNS-320L User Manual page 315

Section 4 - Configuration
Click the Camera checkbox (next to the camera's name) to activate the camera
you want to use as a backup.
Click Save Settings to finish.
The archive table at the bottom will populate as you collect data.
A message will pop up to confirm the configuration. Click Yes to continue and
the DNS-320L starts to backup the IP camera recordings.
D-Link ShareCenter DNS-320L User Manual 309