You can add, modify,
and delete fields in newly defined object data tables until you
perform a save operation (either saving objects back to source drawings
or saving the current drawing). Once you perform a save operation,
only a Superuser can modify the table.
Also, if you have already queried any object from a source drawing,
you cannot modify an object data table.
When you modify an object
data field, AutoCAD Map 3D updates all instances of the field attached
to objects. If the object data table is large, this process can
take a long time.
Renaming and Deleting Tables
If you have Superuser privileges,
you can rename or delete object data tables. if you have already
queried any object from a source drawing, you cannot rename or delete
an object data table .
If you rename a table,
the new name must not duplicate an existing table name.
you delete an object data table from a drawing, the table is deleted
from all attached, active source drawings.