@Override
  public void start() throws StartupException {
    if (config.getWalMode() == WALMode.DISABLE) {
      return;
    }

    try {
      registerScheduleTask(
          config.getDeleteWalFilesPeriodInMs(), config.getDeleteWalFilesPeriodInMs());
    } catch (Exception e) {
      throw new StartupException(this.getID().getName(), e.getMessage());
    }
  }
Region information and WAL node will be removed when using ElasticStrategy.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/wal/WALManager.java