Migrate RHEL7 up to RHEL9 with PostgreSQL

Hi,
Customer need and want to migrate RHEL7 up to RHEL9 using leapp.
Fact is the RHEL7 system is a prod server running PostgreSQL with data on iscsi external storage.

I've already migrated a few systems for this customer with no issue using leapp. Considering this is a production system, I'd like to know what handling and procedure I have to follow for a perfect migration.

Does anyone have experience in this field, any feedback will be appreciated and what would you recommend?

Thank you for your Feedback
Best regards,