You configure an Exception Subprocess.

In SAP Cloud Integration, an Exception Subprocess is used to catch and handle errors during message processing.

It is always triggered by an Error Start Event.

When an error occurs in the main process (e.g., mapping error, adapter error), control is handed to the Exception Subprocess.

Other start events (Message, Escalation, Normal Start) are not valid in an Exception Subprocess.

Hence, the correct event to start the Exception Subprocess is the Error Start Event.