When restoring a collection, such as a PointList, it may not be possible to restore all the collection members. In such a case, the restorer object generates a placeholder for each member that couldn't be restored, in order that the index locations of other objects in the list aren't changed from what they were when the list was persisted.
Each such placeholder is a PIDummy object. It emulates all PI-SDK objects that support the IPIPersist interface. If you try to use most emulated methods, however, the PIDummy object will return the psePIDUMMYERR error. If you refresh (using IRefresh) a collection that has a PIDummy object in it, it will attempt to restore the object it represents and place it in the collection.
The PIDummy object has one unique method: PersistenceString. This is a Read/Write property containing the persistence string of the object that failed to be restored.