All the objects which are modified, after transporting to the current system, will be listed in SPAU and SPDD. SPDD contains the list of all modified Data Dictionary objects, like tables, data elements, domains, view etc. The rest of all the modified repository objects will be listed in SPAU. When you apply a package, a large number of objects are changed. If you have applied any OSS notes to objects in your system, the hot package may overwrite these objects. SPDD is used to identify dictionary objects and SPAU (repository objects), will identify any objects where the hot package is overwriting changes you have made through OSS notes.