CUA - System Refresh

Hello,

I am new to CUA and need help in determining the pre and Post steps for CUA during the System Refresh. The System Refresh is performed on the Child System and after the Refresh my original users and Role assignments have to overwrite the users and Role Assignments of the Copying System.How do I retain my original User data ?

Are their any guidelines to this process ?

I am researching oss and forums,and so far I don't have any clear procedure.

thanks,

Farah