How To Fix CN853 - Activity loses its external processing character

CN853 - Overview

• Message type: E = Error

• Message class: CN - Meldungen für Netzpläne

• Message number: 853

• Message text: Activity loses its external processing character

What causes this issue?

You have changed the control key of the activity. The new control key
specifies that the activity is internally processed.

System Response

The activity will be displayed on the overview for internally processed
activities.

Error message extract from SAP system. Copyright SAP SE.

CN853 - Details

• The SAP error message CN853 ("Activity loses its external processing character") typically occurs in the context of project management and controlling within SAP, particularly when dealing with network activities in Project System (PS) or when managing costs and resources.
  
  Cause:
  The error message CN853 is triggered when an activity that was previously marked for external processing (i.e., it was set up to be processed outside of the SAP system, such as through a vendor or subcontractor) is being changed in a way that removes this external processing characteristic. This can happen due to various reasons, such as:
  
  Change in Activity Type: The activity type may have been changed to one that does not support external processing.
  Modification of Activity Attributes: Changes to the attributes of the activity, such as the assignment of resources or cost elements, can lead to the loss of the external processing characteristic.
  Network Structure Changes: If the network structure is modified