Hello
During a patching process the SPDD and SPAU phases are handled by the development team.
This is because they should be more information about what modifications need to be retained and what not.
Read these links to have a clear understanding.
http://help.sap.com/saphelp_nw70/helpdata/en/2e/6d66587d9011d396b60000e82de14a/frameset.htm
http://help.sap.com/saphelp_nw70/helpdata/en/c8/61ec66e33611d1954b0000e82de14a/content.htm
Regards
RB