Error, I can't access to forum

Lee error

Code:

MyBB has experienced an internal SQL error and cannot continue.

SQL Error:
1 - Can't create/write to file '/tmp/#sql_3b4_0.MYI' (Errcode: 30)
Query:
SELECT t.*, td.* FROM mybb_threadfields_data td LEFT JOIN mybb_threads t ON (t.tid = td.tid) WHERE t.visible=1 AND td.scadenza <= 1439376641 AND td.scadenza > 0 AND t.fid IN ('143') ORDER BY td.scadenza ASC LIMIT 25

and if I try to access to admin:

Code:

MyBB has experienced an internal SQL error and cannot continue.

SQL Error:
29 - File './oecdb/mybb_adminsessions.MYD' not found (Errcode: 30)
Query:
DELETE FROM mybb_adminsessions WHERE uid='1'

Solved, they were corrupted files on the server (but I don't know how they are corrupt)

Corrupt files? You mean corrupt in db or the mybb files? You might need to run a table repair/optimise a bit more often

The hosting fixed file from server, after I reboot the server the website was always offline, I didn't access to SSH, control panel etc. Yesterday I optimised database from ACP, maybe something gone wrong with that?