On the following link:
http://au.autodesk.com/?nd=material&session_material_id=53462
is a text about redo/undo.
There is also a following part:
AcDbDatabase::disableUndoRecording(bool disabling);
AcDbObject::disableUndoRecording(bool disabling);
Both are quite dangerous, especially AcDbDatabase method.
Avoid calling methods that might trigger reactors when UNDO disabled.
what is that?
can't we call db.disableundorecording(true) when needed?
The few times that I used it, which was long ago, I noticed that REDO would not always work when it should have. I can't tell you why however.