La base de données de vignettes

By default, thumbnails are cached in a database in order to speed up browsing. You can disable this behavior (which takes some hard disk space) by going to the Browser tab in the Options dialog.

If you enabled the thumbnail caching then you might want to optimize the database from time to time. When you delete images, thumbnails are not explicitly removed from the database so the space needed for the thumbnail is still occupied on disk but cannot be reused. Running a database optimization will clean up the database and remove all those not-needed-anymore thumbnails.

You can also completely wipe out the database. Of course, if you have not disabled the thumbnail caching then cam2pc will immediately recreate the database file to store new thumbnails. If you delete a database and have not disabled the caching, then cam2pc will ask you if you want to disable it or not.