MySQL: Can't create/write to file '/tmp/#sql_3c6_0.MYI' (Errcode: 2) - What does it even mean?

Question

For some reason my production DB decided to spew out this message. All application calls fail to the DB with the error:

PreparedStatementCallback; SQL [ /*lo         


        

Answer 1

Check permission issues, mysql config.

Also check if you haven't reached disk space, quota limits.

Note: Some systems are limiting number of files (not just space), deleting some old session files helped fixed the issue in my case.