docs: public void registerCallback(TransactionCallback callback)
      {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(this, tc, "registerCallback", "Callback="+callback);
  
          if (_currentTran != null)
          {
              _currentTran.registerCallback(callback);
          }
          else
          {
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) SibTr.debug(this, tc, "No Xid currently associated with this XAResource!");
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(this, tc, "registerCallback");
      }