Whenever a device is successfully reset or created in full-screen operation, the Direct3D object that created the device is marked as owning all adapters on that system. This state is known as exclusive mode, and at this point the Direct3D object owns exclusive mode. Exclusive mode means that devices created by any other Direct3D9 object can neither assume full-screen operation nor allocate video memory. In addition, when a Direct3D9 object assumes exclusive mode, all devices other than the device that went full-screen are placed into the lost state. For information about how to handle lost devices, see Lost Devices (Direct3D 9). [1]