code: private void unregisterObject(DigitalObject obj)
              throws StorageDeviceException {
          String pid = obj.getPid();
          Connection conn = null;
          PreparedStatement st = null;
          try {
              conn = m_connectionPool.getReadWriteConnection();
              String query = "DELETE FROM doRegistry WHERE doPID=?";
              st = conn.prepareStatement(query);
              st.setString(1, pid);
              st.executeUpdate();
  
              //TODO hasModel
              if (obj.hasContentModel(Models.SERVICE_DEPLOYMENT_3_0)) {
                  updateDeploymentMap(obj, conn, true);
              }
          } catch (SQLException sqle) {
              throw new StorageDeviceException(
                      "Unexpected error from SQL database while unregistering object: " +
                              sqle.getMessage(), sqle);
          } finally {
              try {
                  if (st != null) {
                      st.close();
                  }
                  if (conn != null) {
                      m_connectionPool.free(conn);
                  }
              } catch (Exception sqle) {
                  throw new StorageDeviceException(
                          "Unexpected error from SQL database while unregistering object: " +
                                  sqle.getMessage(), sqle);
              } finally {
                  st = null;
              }
          }
      }
docs: Removes an object from the object registry.