Normally, any locks passed to the update are written to the backup file.
If you use the standalone enqueue server and it is configured for replication (profile parameter enque/server/replication), you need to handle the backup file in a different way. It is not important here whether a replication server is active or not.
In productive operation the locks passed to the update process are not written to the backup file, they are only flagged. The locks are only written to the backup file when the standalone enqueue server is shut down.
When the standalone enqueue server is started, it searches for a backup file. If it finds one, it reads it and inserts the locks into the lock table. Afterwards the backup file is emptied (but not deleted). If another replica is found, the locks there are merged with the locks from the backup file.