This works when using Duplicati.CommandLine.RecoveryTool.exe
Thanks
They aren’t informed yet - but: yes. It’s all well planned. I think 
Multiple media (USB, HDD and M-Disk) unencrypted in bank safe. In case of all media failure, or if most recent data are needed, all necessary instructions to get encrypted data from a 2 TB cloud service.
A lot has to be kept in mind in order to keep it simple. Even unencrypted data can be a difficulty (e.g., NTFS ownership, if NTFS… etc…) And difficulties easily lead to: “Aghh, let’s just dump it”.
If you are only using PC2 for restores then you shouldn’t have it scheduled to do backups at all, and I agree its retention should be set to unlimited (although if you aren’t running backups it technically shouldn’t matter). If PC2 has done any changes to the back end, you’ll need to then do a database recreation on PC1! So having PC2 not modify the back end keeps PC1 happy.
Don’t ever set up two computers doing operations on same destination that could change it.
Repair can change the destination to match the database, thus destroying some of the data.
Database on a given computer must match the destination. Two computers, two databases.
Nothing keeps them in sync, so this risks getting complaints about missing and extra files…
Message may ask you to run repair, but that’s the wrong thing to do with invalid configuration.
This is a similar but different risk of conflict. If you shut down while the scheduled backup is running, you would have two Duplicati running at the same time to the same destination. Difference is DB is the same one, so maybe DB access error would error out the whole backup before damage is done. You can test.
Safer plan would be to not have this setup. Less safe might be a run-script-before that checks somehow for another Duplicati backup in progress (or maybe guesses based on times), and stops the backup run.
@drwtsn32 and @ ts678
Thank you for your long and detailed explanation.
I will have to think over the way Duplicati is setup right now.
Let me explain the situation in more detail.
Programs used on PC1 are Microsoft Word and Excel as well as a CAD program and a special calculation program.
Results of work from Microsoft Word or Excel are synchronized to Microsoft OneDrive cloud automatically, this is not purpose of Duplicati.
Purpose of Duplicati is to save the work results from the CAD program and the calculation program.
This can be done manually by starting Duplicati every 1 or 2 hours for example.
Just in case that this is forgotten Duplicati should do backups automatically at a certain time (now set to 17:00 o´clock) and latest at shutdown of PC1.
PC2 is used only to check from time to time, whether it is possible to restore data in case of a fault of PC1. It is possible to assure, that PC2 runs Duplicati only if PC1 is shut down.
Is there a way to prevent PC1 shut down while scheduled or Duplicati manually started is backing up files?
This question is not relevant in the moment. I´m going to do some more tests to see, how Duplicati behaves in my environment.