protected void deleteOutdatedFilesInWALNodes() {
    if (config.getWalMode() == WALMode.DISABLE) {
      return;
    }
    List<WALNode> walNodes = walNodesManager.getNodesSnapshot();
    Map<WALNode, Long> walNode2DiskUsage = new HashMap<>();
    for (WALNode walNode : walNodes) {
      walNode2DiskUsage.put(walNode, walNode.getDiskUsage());
    }
    walNodes.sort(
        (node1, node2) -> Long.compare(walNode2DiskUsage.get(node2), walNode2DiskUsage.get(node1)));
    for (WALNode walNode : walNodes) {
      walNode.deleteOutdatedFiles();
    }
  }
Reboot wal delete thread to hot modify delete wal period.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/wal/WALManager.java