If you have configured your form and process mappings in the system configuration, you will not have to restore those object customizations after the upgrade. If you have customized objects that are not listed in the system configuration, then you must manually restore these objects by importing the XML for these objects.
As a safety measure, Identity Manager automatically saves many of the commonly customized objects to files when you import update.xml. These files are saved to subdirectories in the WEB-INF/savedObjects directory. These subdirectories are named with a time stamp of the time at which the import was performed.