Hi Udo,
in order to move the SCOM DBs you need to follow a particualr procedure. It is a step-by-step guide and contains detailed explainations to each step:
1. First you move the Operational Database:
How to move the Operational database
https://learn.microsoft.com/en-us/system-center/scom/manage-move-opsdb?view=sc-om-2022
2. Right afterwards you move the DataWarehouse
How to move the Reporting data warehouse database
https://learn.microsoft.com/en-us/system-center/scom/manage-move-omdwdb?view=sc-om-2022
Hope I could help you out!
Regards,
----------
(If the reply was helpful please don't forget to upvote or accept as answer, thank you)
Regards,
Stoyan