Flush userdb cache entry

[Tom Sommer]

Hi all

I have a problem when users change quota in SQL, the change is not 
reflected in Dovecot immediately so quota_warning is still triggered on 
some occasions.
I think it's because the quota is stored in userdb, and there is no way 
to flush userdb cache?

Is there a way to flush userdb entries?
What controls userdb cache TTL/size? auth_cache entries?

I can't seem to find any documentation on this, sadly :(

Thanks

--
Tom