Hi Kurro,
if the production stores data that needs to be maintained in the DB, you need to do something more complex (like mapping the data globals in the new NS to the old DB.

If not the safest way to test and also migrate everything is what you are proposing:

• make a backup of the original DB (freeze/thaw or the iris utility from management portal, restore to different location and keep an eye on NOT SETTING SWITCH 10 during restore https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cls... online backup)
• create a new NS copying from the old one
• do the mapping accordingly
• import the upgraded code in the new NS
• disable all the producion pieces (BO / BP / BS) on the new production
• disable the production part (brands) that needs to be migrated on the old version
• enable them on the new version

If something on the new production goes bad, you can easily enable the disabled pieces on the old version, and disable them on the new one.

Pietro