docs: public synchronized void close() throws SQLException {
  
          // Changed to synchronized above because
          // we would not want a sessionProxy.close()
          // operation to occur concurrently with a
          // statementXXX.executeXXX operation.
          if (isInternal || isClosed) {
              return;
          }
          isClosed = true;
  
          if (sessionProxy != null) {
              sessionProxy.close();
          }
          sessionProxy   = null;
          rootWarning    = null;
          connProperties = null;
      }