code: public void truncate() throws IOException {
      getDatabase().checkSecurity(ODatabaseSecurityResources.CLASS, ORole.PERMISSION_UPDATE);
  
      getDatabase().getStorage().callInLock(new Callable<Object>() {
        public Object call() throws Exception {
          for (int id : clusterIds) {
            getDatabase().getStorage().getClusterById(id).truncate();
          }
  
          for (OIndex<?> index : getClassIndexes()) {
            index.clear();
          }
          return null;
        }
      }, true);
    }
docs: Truncates all the clusters the class uses.
  
  @throws IOException