%COMSPEC% /C _rfutil.exe %db% -C roll forward -B 5000 -a %ai%.ai%ai-num%
Normal priority should be fine. That's what it would be if you ran it interactively. You don't want to be below normal, but manually adjusting a process' priority above normal isn't something I'd mess with. It could have unintended consequences, like taking cycles from DB threads.using ProcExp it's showing as the rfutil command running at a 'normal' priority.