Uncaught exception thrown in shutdown function.

PDOException: SQLSTATE[HY000]: General error: 8 attempt to write a readonly database: DELETE FROM {semaphore} WHERE (value = :db_condition_placeholder_0) ; Array ( [:db_condition_placeholder_0] => 16004684085dd1c88a38dd79.55974298 ) in lock_release_all() (line 269 of /web/sites/d.macmurrayranch.com/includes/lock.inc).