Config.xml is heart of weblogic server and if you mess your configuration then how will you recover old configuration.
You don’t need to copy paste file on your handy drive every time when you change configuration.
Weblogic will take care of making sure you have back file maintained and created automatically for you.
Login to weblogic console
Click Domain –> Configuration –> General (Advanced)
Check Configuration Archive Enabled and Count.
true - backups of the configuration will be made during server boot.
Change will take place after you redeploy module or restart the server
it will create following files in domain.