Hi Peter,
z12-17 are marked dirty during the database update (when they changed) z11 is marked dirty once a week z10 is marked dirty twice a month (on the week shifted to z7-9) z7-9 is marked dirty once a month z0-6 re-rendered directly once a month
I found an area that seems immune against updating:
http://osm.t-i.ch/bicycle/map/?zoom=17&lat=47.37909&lon=8.52413&...
I tried both, requesting tiles with /dirty and changing the underlying data, but the tile didn't change since Oct 14th. The other zoom levels changed, so the database is ok.
Any hints?
Regards, Thomas