cmStateIndex is a read-only integer that, together with cmStateGenericClass and cmStateObjClass, uniquely identifies which specific resource instance a given row of the generic state table refers to. An administrator uses it as part of the composite key needed to trace a cmStateOperState or cmStateLastChange value back to one physical port or board. For example, after seeing an alarm reference a particular cmStateIndex, the operator cross-references it with the resource's object class to identify exactly which line or slot changed state.