private TreeSet<Oplog> getSortedOplogs() {
    TreeSet<Oplog> result = new TreeSet<>(
        (Comparator) (arg0, arg1) -> Long
            .signum(((Oplog) arg1).getOplogId() - ((Oplog) arg0).getOplogId()));
    for (Oplog oplog : getAllOplogs()) {
      if (oplog != null) {
        result.add(oplog);
      }
    }
    return result;
  }
set the child to a new oplog
geode-core/src/main/java/org/apache/geode/internal/cache/PersistentOplogSet.java