docs: @Override
      public synchronized void addCallBack(RecoveryLogCallBack callback) {
          if (tc.isEntryEnabled())
              Tr.entry(tc, "addCallBack", callback);
  
          if (_registeredCallbacks == null) {
              _registeredCallbacks = new HashSet<RecoveryLogCallBack>();
          }
  
          _registeredCallbacks.add(callback);
  
          if (tc.isEntryEnabled())
              Tr.exit(tc, "addCallBack");
      }