code: protected void checkAlreadyClosed() throws SISessionUnavailableException
     {
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(this, tc, "checkAlreadyClosed");
        
        if (isClosed())
           throw new SISessionUnavailableException(
              nls.getFormattedMessage("SESSION_CLOSED_SICO1013", null, null)
           );
           
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(this, tc, "checkAlreadyClosed");
     }
docs: Helper method to check if this session is closed and throws the appropriate
  exception if it is.
  
  @throws SISessionUnavailableException if the session has been closed.