In mainframe computing, a relationship that is created in a control unit between a device and a channel path when the device completes a Sense Reserve command. Reserved allegiance causes the control unit to guarantee access (a busy status is not presented) to the device. The device is accessed over the set of channel paths that are associated with the reserved allegiance. Access is for one or more channel programs until the reserved allegiance ends. See also contingent allegiance, implicit allegiance.