How to keep cache_form small I have noticed in mysql that cache_form.MYD table is 14GB. Why did it grow so big? Is it safe to empty it? and how can I avoid this happening in the future?

Thanks
This is a known issue in Drupal 6 and 7 for that matter. It is not cleared when running cron. You can safely delete all rows that has expired.

DELETE FROM {cache_form} WHERE expire &lt; now();


should do the trick.