Ernst,
The respective F-table maintains the shape.len and shape.area information for a Feature Class. But as Vince mentioned, it's not possible to implement this always. The "F" table does not always exist. Native geometry types do not include a Shape.Len and Shape.Area field. We can't create them using an OLE DB connection.
These queries can be used to query the details though, from my experience (sde.Area3 is the FC name):
Select shape.STLength() as length from sde.Area3
Select shape.STArea() as area from sde.Area3
Regards,