& materials to be processed; program will run in the background

What causes this issue?

&V1& materials are to be processed. With this number, processing may
terminate in online mode due to a timeout. For this reason, the system
automatically processes the materials in the background.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

If you nevertheless want the program to run in online mode, you must
cancel the "Execute in background" indicator.

Error message extract from SAP system. Copyright SAP SE.