Turn decay off

Hi @all,

i host a own Rust-Server on Linux-Ubuntu.
All fine at this moment. That means the Server runs stable and fast.
I wan't to turn off the decay from buildings.

I tried a lot of things:
open the console or RustAdmin and enter:
decay.scale 0
decay.scale "0"
decay.scale off <-- shows decay.scale "0" after entering

is saved this with server.writecfg

or add this
+decay.scale "0" in "start_server.sh"
(with reboot etc.)

But if i open ingame the Tool Cupboard, it shows that the timer runs down.
And the walls will remove slowly.
The Support from Facepunch told me "decay.upkeep false" and if that will not work, i must aks you all.

Hope you can help.