You can be notified when new layers are added to the drawing before certain tasks, such as plotting, saving, or restoring a layer state. It is important to be aware of new layers that have been added to a drawing or to an attached xref without your knowledge. You can avoid potential problems such as plotting objects that were added to the drawing by the addition of a new layer.
You can control when a drawing is evaluated for new layers, if at all. You can specify which commands, such as SAVE or PLOT, trigger the program to check the layer list and alert you of new layers. This can include new layers that have been added to attached xrefs.