Put the .viminfo file to an arbitrary location
Ever had the problem to use vim on a read-only root filesystem? In such cases vim keeps naging about beeing unable to write his viminfo file besides it obviously doesn't write this usefull piece of Information.
With the following statement vim can be told to safe this file to /localdisk/root/.viminfo (besides some other settings).
set viminfo='50,<1000,s100,:0,n/localdisk/root/.viminfo