ALTER TABLE, OPTIMIZE TABLE, ANALYZE TABLE and REPAIR TABLE doesn't work reliable with table on which one are executing INSERT DELAYED statements at the same time the command is running. Symptoms are lockups or crashed tables. Proposed fix in MySQL 4.0 When doing an open_ltable() (Table with lock) for any of the above commands, it should be done in the following way: - open table - mark in shared structure that insert delayed is not allowed - Kill insert-delayed thread for table if it exists This will flush all pending rows to disk. - Get lock for table - Execute operation - Close table - Send signal to possible insert-delayed-thread that it can continue. - As long as the shared struct is marked, all tries to do TL_LOCK_DELAYED should be changed to TL_WRITE_LOW_PRIORITY. This will ensure that open_ltable() in handle_delay_insert() will wait until the statement has executed.