What is error 1021 - Disk full in database related to?

Question

MySQL

An ordinary day I worked on the site and suddenly this popped up:

At the same time, I didn’t go into the database at all, I didn’t do anything at all except changing styles. Can't access admin. Hosting freaking gino. Joomla 3
SQL file weighs 20.8 megabytes why disk full... xs...

Answer 1

trying to create a temporary file /tmp/#... for sorting OS says no places
maybe /tmp mounted in tmpfs while the RAM was full

Answer 2

Maybe it's worth looking at df -h on the server?