Plesk is inaccessible: Can’t create/write to file Errcode: 17, query was: DESCRIBE `sessions`

Symptoms

Plesk is inaccessible with the following error:

PLESK_INFO: Server Error
500
PleskExceptionDatabase
DB query failed: SQLSTATE[HY000]: General error: 1 Can’t create/write to file ‘/tmp/#sql_434_0.MYD’ (Errcode: 17), query was: DESCRIBE `sessions`

Cause

Temporary file cannot be written to because it was not removed from a past session and it’s unwritable by the current session

Resolution

1. Connect to the server via SSH

2. Restart MySQL server:

   # service mariadb restart | service mysqld restart | service mysql restart

   Note: In case the issue reoccurs, MySQL server parameters like innodb_ buffer_ pool_size should be optimized in accordance with the server load.