If a dimension is driven by a relation, the dimension cannot be modified directly. If you try to do so, Creo Parametric displays an error message.

For example, if you enter the relation d0=d1+d2, you cannot modify d0 directly. You must modify d1 or d2, or edit the relation in order to change the value of d0.

If a dimension symbol is modified, the change is automatically reflected in the relation file.