How to make sure consistency when backup a volume?

If an app writes data into the volume when the restic is running, how to make sure the backup data is right?

You can use Stash hooks to freeze the file system before backup and unfreeze after backup. Ref: https://stash.run/docs/v2021.11.24/guides/latest/hooks/overview/

Thank you for your answer. I've read the ref carefully. Now I wonder if freezing the file system will affect the use of app when the backup process continues for a long time.