[robweber]

robweber:
Thanks for a really fast answer. So it is best to do both, then I`ll do that.
If I back up the whole db file, in the last XBMC 11, do a fresh install of the whole computer,
with the new XBMC 12, will it then work to use the backup?

I wonder, because the db file name is changing with every new release if I have understood it right,
And it seems this way in the DB folder.

Thnaks for the help so far.

Backing up your user data (including DB files) before you upgrade from v11 to v12 is 100% a smart idea. You are right though that what will happen is that XBMC will create new DB files, with a corresponding database version number. If you old DB files are present when this happens it will upgrade your database, copying data from the previous DB to the new one. If you old DB files are not present it will simply create a new, blank database.

If you wipe your computer, then install XBMC v12 from scratch you will not have any userdata present, so you'll get a bunch of blank database and setting files when you first turn xbmc on. Restoring your backup will not help the database since the new v12 DB will already be created and it will no longer look for the old one. You do have a few options here though for an upgrade path - while still retaining a backup of your information in the event you want to restore back to v11.

1) Backup XBMC v11. Then, rename the backup folder but keep it in the same directory. I would just give it the previous date. Then do an in place upgrade to XBMC v12. This will upgrade your database and add the necessary v12 changes to your other folders. Then do another backup of your v12 data. After you wipe your computer you can do a restore of your v12 backup to get all your data back into the now blank xbmc folder. This will still let you retain your v11 backup in the event you need to revert to that version of xbmc.

2) Backup XBMC v11. Wipe your computer and upgrade to v12. Once v12 has started do a restore of your v11 backup. After this completes, delete the v12 database files and restart xbmc. This will cause xbmc to recreate them, but this time it will see your old v11 database and copy it over during the upgrade.

This is kind of a round about process. The fact that you want to wipe your computer makes it a bit more complicated than if you were doing an in-place upgrade.