This section introduces the concept of SAP Shadow Notes.
During the zero-downtime run, you may have to apply SAP Notes on the shadow repository. Those SAP Notes are often referred to as "Shadow Notes". SUM stops in phase MAIN_SHDIMP/SUBMOD_SHD2_RUN/CHECK4NOTES_TOOL_SHD2
showing a respective dialog listing the required SAP Notes.
Shadow Repository
- The shadow repository is based on the target release.
- For support and feature package updates, the shadow repository is built up from the source release.
- In case of release upgrades, the shadow repository is created from the SAP export media.
- SAP Notes for the shadow system deliver code changes that are required to fix issues in the export media or target feature/support package.

Digitally signed SAP Notes
Note that in ABAP systems, by default, the SAP Note Assistant must be capable of downloading and consuming digitally signed SAP Notes using HTTP connection as this type of SAP Note is now mandatory. The SAP Note Assistant of the source system needs to be enabled to work with digitally signed SAP Notes.
If the source system is not enabled to work with digitally signed SAP Notes, you can manually download the requested SAP Notes from SAP Support Portal and upload them in the shadow system.