If you are on a hosting provider with a small DB size requirement, or one that doesn't do traditional database backups that auto-truncate the logs you can get this issue due to natural churn on some of the tables in the DB.

You may reach out to them and ask if you can change to "Simple Loging" rather than full which will help the file not bloat. Or have them do regular backups with the truncation of logs.

NOTE: If you change to simple logging it DOES impact the recovery model though so it should be discussed with your hosting provider to ensure that it doesn't put you at risk.

Many thanks Mitchel, I'll ask my support folks to give it a go and see what happens.

A quick update Mitchel - this is the response from my hosting support. Hopefully all good news going forward :-)

Setting the 'Recovery Model' to Simple is what we've been previously doing to rectify your DNN databases for other sites historically, but this xxxxx.com database got reverted to 'Full' recovery model.
We've now set this database Recovery Model to Simple again, and this time set a trigger on the database server that should lock that Simple model in place (if any attempt is made to revert that to Full, it should be blocked)
So hopefully that should now resolve this going forward.

Hi Mitchel, sadly back again with the same issue.  

My hosting support folks have adjusted the 'trigger' to set the logging back to simple with an extra fail-safe, so if the recovery model does get changed by 'something' more than once the trigger knows to do a double recheck and revert the recovery model back to Simple.

Despite this the database still bloated and stopped the site.

If this sheds any light this bloating happens seemingly whenever they have an increase in members (tens tops, not hundreds or thousands).  They have an annual conference and at this time of year they have the majority of their members rejoin or affiliates sign up for access to the conference.

Would this have an effect causing the database to bloat?

Bye for now
Malcolm

As an update my absolute superstar hosting support folks have now setup an Agent Job which will automatically check your databases every hour of every day and if necessary revert the Recovery Model back to Simple.

Hopefully this works and I don't post back on this thread and this is helpful to others suffering with this issue :-)