DB maintenance optimizes administrator-selected tables in the database during regular cron.php executions. For MyISAM tables, OPTIMIZE TABLE repairs a table if it has deleted or split rows, sorts table indexes, and updates table statistics. For BDB and InnoDB, OPTIMIZE rebuilds the table. Note, MySQL locks tables during the time OPTIMIZE TABLE is running. Optionally the user can select to attempt a REPAIR TABLE in the event errors are found during attempted OPTIMIZE TABLE. If you enable this ensure you have proper working backups.
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