util_execute migrate - question on usage

I need to upgrade SAPDB 7.3.35 to the latest as part of a content server system copy + upgrade.

I found a thread listing these steps....my question is regarding util_execute migrate, does it modify the existing DB or does it modify the Backup only ? I do not want to make any changes to the existing DB,

open dbmgui (1st edition)

>> create a new backup medium target

>> take instance offline

>> take instance to admin

>> menu: Instance->command line

>>exec "util_execute migrate"

>> exec "util_connect"

>> exec "backup_start <newly created medium name>"

>> exec "util_release"

>> exec "db_offline"

thanks.

Linwood