See also:

Malfunction
A message is displayed in the instrument cluster. HDC is not available, e.g., due to elevated brake temperatures. ...

The concept
The parking brake is primarily intended to prevent the vehicle from rolling while parked; it brakes the rear wheels. ...

Vehicle storage
If your vehicle is to be decommissioned for longer than three months, your BMW center or a workshop that operates according to BMW specifications will be glad to advise you. ...