as far as I know the network moves with the controller and all infomations are stored on it. If there is a problem its mostly how the software (OH) communicates with the controller and read/writes informations.
I wouldn’t recommend it as its much work.
Personally, I’d do a fresh install of OH3 instead of an upgrade. Anecdotally, it seems to me that people have had more issues with upgrades.
As Bruce notes, the security key isn’t stored in the controller. So if you have secure devices and do install fresh, you should write it down from your old installation and paste it into your Z-Wave Serial Controller thing’s configuration (you’ll need to view Advanced Settings). You should do this before adding any secure Z-Wave devices, but you can recover if you miss this step (I did). If you don’t have any securely included devices at the moment, this isn’t necessary.
To speed device discovery, you can also copy over the XML files from your old installation.
Which files did you copy? userdata/zwave/network_*__node*.xml?
I’ve got the issue that I did a fresh install of OpenHAB3 to migrate from openHAB2 and I’ve got a bunch of battery operated zwave devices. They were not found in the Inbox until I ran a scan but they’re still unknown. Waking them up did not work. Do I really have to carry them (physically) to the zwave controller and wake them up there?
Yes, those are the files you need, but it’s an optional step.
Battery-powered devices usually need to be woken multiple times. Or, as @Sascha_Billian says, just wait on them. One of my ZWave sensors tends to be finicky, and after a few days it just started working on its own.
If they aren’t recognized after awhile, you may need to remove and rediscover the things in OH3 (do not exclude them from your controller).
Don’t wait, then. Try manually waking the devices or removing them, adding your old XML files, and re-adding them.
ZWave isn’t perfect, but I’ve personally found that it’s great once everything is paired. I have more regular trouble with my WiFi devices, which are also dependent on my WiFi router. I don’t have any ZigBee devices for comparison, but I’ve heard good things.