code: int addRef()
    {
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
        SibTr.entry(tc, "addRef");
  
      int ret = NOP;
  
      // If this is a new subscription, then the operation is to subscribe.
  
      if (_refCount++ == 0)
        ret = SUBSCRIBE;
  
      checkRefCount();
  
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
        SibTr.exit(tc, "addRef", String.valueOf(ret) +":"+ String.valueOf(_refCount));
  
      return ret;
    }
docs: Adds a reference to the subscription.
  
  
  @return The operation represented by the addition of the reference.