Authors: Nir Shervi & Noa Shimon
The most straightforward migration is to set up a working instance of the version you need but with no configuration or data on it yet, just a blank instance, no artifacts, and default data in the database (new database, not pointing to the old DB).
After you have this working the way you want, you can work on migrating from the old instance to the new instance using a complete system export from the old and then importing on the latest.
You can switch your DNS back to the old instance if things do not work.
The above is the most straightforward procedure but would involve some downtime if you wanted to ensure both instances contain the same data at the time of the cut-over.
We have some things you can do to reduce or even eliminate downtime.