How to hand over data to a background service

The background for that time has already run.  It's too late.  Also did you switch to setValue from setProperty?  With setProperty, that only gets written when the main app exits.

First, to make things more clear: This is a data field App Type. In initialize() for Application.AppBase I inialize the value with one Storage.setValue("MyValue", 1)

I write the property each time background data comes in during onBackgroundData().

I read the value with Storage.getValue("MyValue") during the backgrounds System.ServiceDelegate onTemporalEvent().

The value is always one, no matter how many temporal events there have been. I use System.println calls to show the values during usage of the data field. I can see that the value for the app already changes a couple of temporal events ago, but the background service still retrieves 1 as Value from getValue.

Are you letting the background run "naturally" or are you forcing it in the sim to run more often?

I'm forcing them in the sim to run more often.

Let it run on it's own.  Also, add println() calls for things like when you do the setValue() and onTemporalEvent() starts.

I will check the natural runs. I already have println calls for almost evey little step, because the issue is driving me nuts :)

Presumably there’s information your foreground process has that the background process doesn’t. So that the background process can’t just set the value directly itself.