code: public boolean updateUser (final User user)
          throws PersistenceException
      {
          if (!user.getDirtyMask().isModified()) {
              // nothing doing!
              return false;
          }
          update(_utable, user, user.getDirtyMask());
          return true;
      }
docs: Updates a user that was previously fetched from the repository.  Only fields that have been
  modified since it was loaded will be written to the database and those fields will
  subsequently be marked clean once again.
  
  @return true if the record was updated, false if the update was skipped because no fields in
  the user record were modified.