It is quite useful. However, I have to warn people that the zwave logs do not log ALL of the hubs zwave traffic - so it shouldn't be used as "the source of truth" necessarily.
But the events that do show up there can yield quite a lot of information, so it is still useful.
@lewis.heidrick - can you giver an example of how you've used info in the log to suss out a problem/issue? Just curious as I'm going to be moving over from ST to C7 soon (hub is here, but being careful to prepare and not rush it) and would like to know more about what you found in the logs that helped.
Thanks!
I pulled up the regular log, the zwave log, and the z-wave details page. Performed a z-wave repair and watched each for issues. On the z-wave details page page you have to refresh it occasionally to see it update. While pairing I watched the z-wave log for communication from the device and confirmed that pairing completed successfully for each. Caught a couple of dome motion sensors that looked like they paired after the timer ran out but they didn't actually complete. Had one rule that was misfiring in the kitchen and spamming the regular log with it trying to turn off the lights repeatedly. Deleted the rule and recreated to resolve. Also used the signal strength to tell if it was good. Had one contact sensor that was spamming the z-wave log. Deleted and recreated to resolve that.
I have two devices showing up that I can't figure out what they are...
This is from the Z-Wave Details page.
Clicking refresh or discover doesn't change anything.
0x01 is the hub itself.
0x22 is a device that didn't finish inclusion. Click the Discover button and see if it gathers the needed info.
Just for reference, the C-7 hub reserves node addresses 1-5 so the first Device Included will get Node #6
Tried the discover but it didn't change.
If it's a device that's powered down then, yea, Discover won't.. discover it. The Node number might give you a hint.. look at the devices either side of that number and you may remember what was going on at that time.. maybe an "Initializing" that never completed, you started over and now its device 0x23??
Failed discovery should result in a Fail and the Remove button should appear near the Refresh button. Since maybe it doesn't exist, you'll end up doing a Force Remove (not encouraged) and have to let the overnight cleanup do it's work. 
Lol I have too many light switches... Took me 20 minutes to find which one it was. All cleared up now.
How do you view this log?
It is only available on the c7 hub. But on that you go to settings, Z-Wave details, Z-Wave log.
I have the C7. I was afraid you were going to say that. My Z-Wave log page is empty. Always. Even after waiting hours, nothing ever shows up on that page.
I've seen that before. Consider doing a graceful shutdown, pull the power cord for 30s, and boot back up.
Yep, I've tried that. No joy. Interestingly, the zigbee log page works fine.
Don't know then. I've always been able to get it to work after fully resetting the system.
It's a live log... it's empty when you first open it.. it grows as ZWave messages occur.
It 'deserves' the same message as live logging: "--- Live Log Started, waiting for events ---"
I understand that. That's why I said above that I've waited hours and nothing ever shows up on that page. The live log page works (as far as I can tell) and so does the zigbee log.
I started mine to verify my words were accurate and indeed, I began getting results after a minute or two. I understand that 'works for ME' isn't a great help.. but it does say that you're correct in that it SHOULD work as described.
This is probably crazy, but you could try excluding and then including an existing Z-Wave device on your system, and see if maybe that breaks the log jam?
Download the Hubitat app
