code: protected void checkValid() throws SISessionUnavailableException {
  
          if (!_parentConnection.isValid()) {
  
              final SISessionUnavailableException exception = new SISessionUnavailableException(
                      NLS.getString("INVALID_SESSION_CWSIV0200"));
              if (TRACE.isEventEnabled()) {
                  SibTr.exception(this, TRACE, exception);
              }
              throw exception;
  
          }
  
      }
docs: Checks that the parent connection has not been invalidated by the
  connection manager.
  
  @throws SISessionUnavailableException
  if the connection has been invalidated