The better way would be...incase if you know that you already have a login for the orphaned user. You can use this command alter user <username> with login = <login name>. This is a much better fix then what you're using.

As far as "auto_fix" is concerned, use this if your sure enough that sql server login name is the same as the orphaned user of the database being mapped (in simple terms login name = user name)

Incase, if you don't already have an existing login, you can create one by using this command

exec sp_change_users_login @action = 'auto_fix', @usernamepattern = 'some user name', @login = 'login name', @password = 'specify a strong password'

I hope this piece of info helps!!!

Regards,

Faisal