Saturated database

Hello
I have a problem with the Owncloud 2.8.1 database (build 4157)
I have 3 tables that keep saturating my database.
These are the oc_activity, oc_filecache and oc_file_locks table
Why are three tables saturated like my database?

oc_filecache is as big as your ownCloud instance. Many files results in big oc_filecache.

oc_activity can be controlled with a parameter in the config.php:
Apps Config.php Parameters :: ownCloud Documentation
(and it needs Cronjob running, see How to empty the oc_activity table?)

oc_file_locks maybe also an issue with Cronjob not running reliable, maybe check Lock files issues - 65K entries in table oc_file_locks

More information about Cronjobs:
Background Jobs :: ownCloud Documentation