code: public void addPersistentRef()
      {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(this, tc, "addPersistentRef");
  
          // We have at least one durable reference so the message
          // must maintain its level of persistence
          maintainPersistence = 1;
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(this, tc, "addPersistentRef");
      }
docs: Note the existence of a persistent reference