Originally posted by: tony.evans
smit -> Will do 99% of what you need and will prevent you making any mistakes. Will also ensure everything that needs to be changed can be changed.
chuser / chgroup / chsec -> Will do 99.9% of what you need to do, makes it hard to break things but not impossible and requires you to be aware of what settings are in what files.
vi -> will do 100% of what you need to do, but you have to know what files to change, which files link together and the chances of breaking something are much higher.
And if you have to ask, then the chances of breaking something are very high indeed.