I imagine someone else can chime in who has actually tried this or looked into it more, but I'll say a couple things anyway. Take this with a grain of salt because my input here is partially guessing what the best approach is and some experience with manually upgrading and downgrading Blue Prism versions, but except for one situation in the past I've never had to downgrade before.
1. You should plan to replace the entire database if the upgrade fails and corrupts the database OR if the upgrade succeeds but you decide you want to revert. I'm not a DBA and I have no experience with rollbacks. If you don't have a DBA helping with this who understands those things, I would say to simply take a backup of the entire DB which is standard practice in Blue Prism upgrades anyway, and then just delete the corrupted database and create the database again using the backup if needed.
2. The license should 100% be backed up already. If you do not have the license files backed up somewhere, you should do this, for both your v6 license(s) and your v7 license(s). Plus it's easy to just back up those files and install/import them into Blue Prism environments as needed.
3. The last thing I'll say is that I personally would recommend having a separate BP environment that you use specifically as a sandbox for upgrading Blue Prism versions. That adds a bit of infrastructure costs, but I've seen this be extremely useful, and then you can test out upgrading with no fear of the consequences for the first upgrade. You still should back things up of course, but it can be good for evaluating a new version and you can import releases into it and verify things are working there before upgrading any of your other environments.
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Dave Morris
Cano Ai
Atlanta, GA
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Dave Morris, 3Ci at Southern Company