public synchronized <T> IPersistentSet<T> createSet() {
		if (!opened) {
			throw new StorageError(StorageError.STORAGE_NOT_OPENED);
		}

		IPersistentSet<T> set = alternativeBtree ? (IPersistentSet<T>) new AltPersistentSet<T>(
				true) : (IPersistentSet<T>) new PersistentSet<T>(true);
		set.assignOid(this, 0, false);
		return set;
	}