Upgrade failed but worked perfectly on our other site. Any ideas as to what might cause this database error? And how it might be fixed.

~~~ Thank you. ~~~

Query:

SELECT `tk`.`ID` AS `id`, `tk`.`IDCategory` AS `category_id`, `tk`.`Key` AS `key`, `ts`.`String` AS `string` FROM `sys_localization_keys` AS `tk` LEFT JOIN `sys_localization_strings` AS `ts` ON `tk`.`ID`=`ts`.`IDKey` WHERE 1 AND `ts`.`IDLanguage`=:language_id ORDER BY `tk`.`Key` ASC

Mysql error:

Can't create/write to file '/tmp/MYY6NQFl' (Errcode: 5 "Input/output error")

Location:

The error was found in getAllWithKey function in the file /home/xyz/public_html/xyz.org/inc/classes/BxDolLanguagesQuery.php at line 333.

collation_connection:

utf8mb4_unicode_ci