Physical subcells that contain extracted devices or subcells that have no connection to the circuit may be present. Since the electrical hierarchy is used for recursion, these are not detected in the traversal, since they have no representation in the schematic and no connection to the circuit. However they are checked for explicitly. If any such subcells are found, they will be listed, but otherwise ignored, unless the LvsFailNoConnect variable is set, in which case LVS will fail on the presence of such cells.