code: protected String addMessageNoCaching(InternalEvent msg, EngineDataAccess edao, String msgid) throws SQLException {
          if (cacheOption==CACHE_ONLY) {
              return null;
          } else {    // CACHE_ON/CACHE_OFF
              edao.persistInternalEvent(msgid, msg.toXml());
              return msgid;
          }
      }
docs: /*
  for InternalMessengerJms short delay only