This read-create StorageType object reports permanent(4) for a programmable tone belonging to a system built-in tone plan (in which case only cvtcProgrammableToneDuration remains modifiable), or nonVolatile(3) for one belonging to a user-defined tone plan. Administrators use it to understand how much of a given built-in tone's definition they're actually allowed to customize versus which tones are fully user-editable. For example, an admin trying to change a built-in tone's frequency would find it isn't permitted once this object reports permanent(4), leaving only its duration adjustable.