Found an answer here: How does asbackup ensure the consistent of the backup on running server? - #2 by Albot
As it finds a record, it will be recorded into the backup file → So no record → no data for backup. 
Found an answer here: How does asbackup ensure the consistent of the backup on running server? - #2 by Albot
As it finds a record, it will be recorded into the backup file → So no record → no data for backup.