docs: private void restoreBackupIncremental() {
  
          try {
              if (fa.isStreamElement(fileName + ".backup")) {
                  RAShadowFile.restoreFile(fileName + ".backup",
                                           fileName + ".data");
              } else {
  /*
                  // this is to ensure file has been written fully but it is not necessary
                  // as semantics dictate that if a backup does not exist, the file
                  // was never changed or was fully written to
                  if (FileUtil.exists(cacheFileName)) {
                      int flags = DataFileCache.getFlags(cacheFileName);
  
                      if (!BitMap.isSet(flags, DataFileCache.FLAG_ISSAVED)) {
                          FileUtil.delete(cacheFileName);
                      }
                  }
  */
              }
  
              deleteBackup();
          } catch (IOException e) {
              throw Error.error(ErrorCode.FILE_IO_ERROR, fileName + ".backup");
          }
      }