Will there be any impact at time of switchover (of application) when needed? If yes, how to overcome it.
There is no impact at the time of the switchover.
Maintenance Wizard FAQ [ID 405263.1]
If you do not have a backup, you could simply copy the file from the primary node and edit it manually. Or you could run AutoConfig on the standby node at the time of the switchover and it will create the file for you -- About Oracle Applications DBA Minipack 11i.AD.I [ID 233044.1]