public List<Integer> getSchemaRegionIds() {
    List<Integer> schemaRegionIds = new ArrayList<>();
    getPartitionManager()
        .getSchemaRegionIds(
            new ArrayList<>(quotaInfo.getSpaceQuotaLimit().keySet()), schemaRegionIdMap);
    schemaRegionIdMap.values().forEach(schemaRegionIds::addAll);
    return schemaRegionIds;
  }
If the new quota is smaller than the quota already used, the setting fails.
iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/manager/ClusterQuotaManager.java