What is SPAU / SPDD
After the Support Pack or Enhancement Pack implementation existing objects of the SAP standard are overwritten with the objects redelivered.
Many a times customers change standard code to suit their requirements. During the upgrade process, Instead of just overwriting the objects, SAP gives an option for customers to resolve these objects manually by showing the objects in the transactions SPAU/SDD.
Data Dictionary objects which have prior changes before the upgrade are shown in transaction SPDD. DD objects resolution during the upgrade is critical and there could also be a need to resolve the SPDD objects during the upgrade.
Program related objects like Programs, Function Modules, Classes, Includes etc are shown up in transaction SPAU. SPAU resolution can be done after the upgrade and there could be a need for functional and technical inputs to resolve the objects.
This helps customer retain the objects modified in a previous release. These transactions allow customers to enter their modifications into the corresponding new objects being delivered at upgrade. The Modification Assistant supports this process of adopting customer modifications.
For eg – Customer has added some lines of code to meet a functionality and perhaps SAP has released this functionality with an upgrade. The person who resolves the SPAU, should act accordingly whether to keep those customer specific lines or not.