Bug: SDO_GEOMETRY NULL features converted to NIL when copied
Copying a feature class from one ArcSDE SDO_GEOMETRY feature class to another converts features with NULL geometry to features with NIL geometry. ArcSDE represents NIL geometries in Oracle Spatial feature classes as "SDO_GEOMETRY(NULL, NULL, NULL, NULL, NULL)". ArcSDE represents NULL feature as simply a NULL in the SDO_GEOMETRY column.
Oracle’s geometry validation function SDO_UTIL.VALIDATE_GEOMETRY_WITH_CONTEXT reports both of these representations as NULL.
Neither NIL or NULL geometries contain any vertices. The difference only affects users that differentiate between NIL and NULL geometries, or depend on NULL SDO_GEOMETRY features to be represented as a NULL.
This is a known issue. It is fixed in ArcSDE 9.2 SP1.
After copying feature a feature class, update the features from NIL to NULL using SQL, assuming that the features to be updated can be identified by their attribute columns.