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: 145 Table './educompdb/semaphore' is marked as crashed and should be repaired: SELECT expire, value FROM {semaphore} WHERE name = :name; Array ( [:name] => cron ) in lock_may_be_available() (line 168 of /var/www/html/includes/lock.inc).