code: protected void markInvalid()
     {
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(this, tc,"markInvalid");
        invalid = true;
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(this, tc,"markInvalid");
     }
docs: Marks the enumeration as invalid.  This is called once the asynchronous
  consumer callback returns to ensure that this locked message enumeration
  cannot be used from outside the callback.