/dev/dm-0 was full (root). MySQL wouldn’t start which meant my OwnCloud server was dead in the water (and not good cause I needed it).
This saved my skin: https://www.rootusers.com/how-to-increase-the-size-of-a-linux-lvm-by-expanding-the-virtual-machine-disk/
I followed it verbatim after trying many, many different suggestions on various websites. MySQL service starts and back in business. 🙂
Since initially writing this post, I have begun using this method: https://www.rootusers.com/use-gparted-to-increase-disk-size-of-a-linux-native-partition/