[support] Cron and clearing caches to update field data..

Hi,

Can someone explain what running the drupal cron job does and at what intervals??

Here is the situation.. We are updating a particular field directly in the database from another source.. This is working fine but the issue is that the updated information doesn't show on the site straight away..

I have cron running every hour and have the cache lifetimes on the performance page set to 10 min but even after waiting an hour and a cron run the page still isn't always updated with the new value of the field.. Sometimes it is and sometimes it isn't..

The only way I have found to "force" an update is to clear all the caches but this seems like a massive overkill..

If I can find out when it will update on its own I can set the user expectations so they know they have to wait that long for the data to be updated..

Thanks for any information..