In ArcGIS 9.x if a Feature Class is registered with a Class Extension the CLSID of the extension is recorded in a table in the sde schema called sde.GDB_OBJECTCLASSES (EXTCLSID field).
However in ArcGIS 10 there is no such table, and I can't find anything comparable in an SDE 10 database. I assume this information must now be stored in the data server's registry, but I am not sure where to start.
I am trying to debug issues apparently caused by an upgraded (ArcGIS v10) Class Extension updating data in a Feature Class originally registered with a v9.3 Class Extension and held in a v9.3 SDE database (both versions of the extension share the same GUID), so any insight on this would be much appreciated.