SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.1.5): Invalid SQL: DELETE FROM bb2_sessions WHERE userid='0' AND ipaddress = '18.206.238.176' AND useragent = 'CCBot/2.0 (https://commoncrawl.org/faq/)'
mysql error: Out of resources when opening file './usr_web1_15/bb2_sessions.MYD' (Errcode: 24)
mysql error number: 23
mysql version: 5.5.47-0+deb6u1-log
php version: 5.3.3-7+squeeze29
Date: 04.07.2020 @ 07:41
Script: /thread.php?threadid=936
Referer: