code: public void clearDataListState(String key) {
          Map<String, Object> sessionMap = getFacesContext().getExternalContext().getSessionMap();
          Map<String, TableState> dtState = (Map) sessionMap.get(Constants.DATALIST_STATE);
          if (dtState != null) {
              dtState.remove(key);
          }
      }
docs: Removes the multiViewState for one specific DataList within the current session.
  @param key Key of the DataList. See {@link org.primefaces.component.datalist.DataList#getDataListState(boolean)}} for the namebuild of this key.