How to make/clear free space in a Drupal MySQL database?

To clear out free space in your Drupal's database -- typically a MySQL installation -- you can generally empty the cache tables. Many versions of Drupal include a bug in which the cache_form table is not cleared, causing it to grow to be quite large in size over time. Note that emptying these tables could have a short-term effect on your website; for example, clearing cache_form will clear any forms currently being filled out on the website.

Drupal logo

To clear these tables you can use a common tool such as phpMyAdmin to administer your MySQL database. There may also be Drupal modules available which can do this for you as part of the site's maintenance cron tasks.