Home-assistant_v2.db not found after changing configuration file

Dears

I have a home assistant installed on a raspberry. I’m doing some tries as I just started working on it. I modified my configuration file with the following lines:

recorder:
  purge_keep_days: 5
  db_url: sqlite:////ha_db_backup/

As I do not see any error while restarting HA I was just wondering as I cannot see the home-assistant_v2.db anywhere. Neither in /ha_db_backup (a usb stick I mounted formerly) nor in the config folder…

thx