code: void mark()
    {
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
      {
        SibTr.entry(tc, "mark");
        SibTr.exit(tc, "mark");
      }
  
      _marked = true;
    }
docs: Marks this object.
  
  Used for deciding if this object is to be deleted.
  The object is marked, the proxies are all reregistered.
  If there is a mark still left, then this proxy can be deleted.