This read-only PrimServiceState value reports the overall primary service state of the Common Controller, distinguishing out-of-service (OOS), where complete service cannot be provided, from in-service (IS), where the controller operates normally even if a non-service-affecting test or minor error exists. It gives an administrator the single most important health indicator for the controller card. For example, seeing this attribute change to OOS would immediately tell an operator that the headend has lost its controlling card and needs urgent attention.