When you’re getting the message “General error: 3 Error writing file /tmp/xyz” while using Matomo Analytics, the reason is that the disk space is full on your /tmp partition. The MySQL/MariaDB database is trying to create new files in the folder /tmp but the disk space is full, so we recommend to increase the size of the /tmp partition (or another path may be used as configured in your MySQL setting tmpdir).
Once you’ve increased the disk space of your tmp directory, your Matomo page should then load successfully.

Alternatively you may also get errors like “Got error 28 from storage engine” which means that one of the disks on which the MySQL databases are stored is full. To solve this issue, check which partition is full and then allocate more space to this partition. For example on Linux you can check which partition is full by running the command df -h.