When the hard drive is full, the system will overwrite the oldest recordings by default. This is recommended, as it makes sure that your system will continue to record without any input from you. You can also set the system to stop recording once the hard drive is full.
To configure hard drive overwrite:
From the Live View display, right-click to open the Quick Menu, then click Main Menu.
Click STORAGE, then click the BASIC tab.
Ensure HDD Full is set to Overwrite to overwrite the oldest recordings when the hard drive is full.
NOTE: Select Stop Record for the system to stop recording when the hard drive is full.