MyBB Community Forums

my database size is now 3gb and i notice that mybb_sessions is using 2gb, is it okey to empty that table without affecting my forum? they said that mybb clears sessions by default but i dont think do

you can empty sessions table. see this thread for related information.
however it appears that Daily Cleanup task is not running on your forum.

or you can delete only guest sessions (uid='0'):

Guest sessions are deleted in ./inc/tasks/dailycleanup.php

	// Clear out sessions older than 24h
	$cut = TIME_NOW-60*60*24;
	$db->delete_query("sessions", "uid='0' AND time < '{$cut}'");