Error message

• Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/includes/common.inc:2791) in drupal_send_headers() (line 1499 of /var/www/html/includes/bootstrap.inc).
• PDOException: SQLSTATE[HY000]: General error: 126 Incorrect key file for table './educompdb/semaphore.MYI'; try to repair it: DELETE FROM {semaphore} WHERE (name = :db_condition_placeholder_0) AND (value = :db_condition_placeholder_1) ; Array ( [:db_condition_placeholder_0] => cron [:db_condition_placeholder_1] => 18577374486333f7aaade202.61710683 ) in lock_release() (line 254 of /var/www/html/includes/lock.inc).