Any way to find out what impact certain "no" commands have on IOS?

[nustak1]

We want to do some config cleanup on a lot of routers and I'm trying to make it as quick and generic as possible. For example: removing IPv6 on BGP. Issuing the 'no address-family ipv6' under router bgp config also removes the neighbors under address-family ipv6. Is there any way to find out how this works for other commands, or is that just trial & error?

[MHM Cisco World]

Sure no address family will remove any subcommand under it'

And it case for all IOS command 

If you do no in command then all subcommand will remove.

It trial and error there is no way know whcih command will effect by add NO to other command.

MHM