How To Fix CN839 - Start and target activities cannot be identical

SAP Error Message - Details

• Message type: E = Error

• Message class: CN - Meldungen für Netzpläne

• Message number: 839

• Message text: Start and target activities cannot be identical

What causes this issue?

You have entered the same activity number for both the beginning and
target activities.
When you include this standard network you would create a loop.

System Response

INCLUDE 'NA_ALLG_NOVERARBEITUNG' OBJECT DOKU ID TX

How to fix this error?

Enter a different activity number for the beginning and target
activities.

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message CN839 - Start and target activities cannot be identical ?

  The SAP error message CN839 ("Start and target activities cannot be identical") typically occurs in the context of project management or network planning within SAP, particularly when working with activities in a project or network. This error indicates that the system has detected an attempt to link an activity to itself, which is not allowed.
  Cause:
  The error arises when:
  
  You are trying to create a relationship (dependency) between an activity and itself. For example, if you attempt to set the predecessor and successor of an activity to be the same activity, SAP will throw this error.
  This can happen during the creation or modification of a project network or when defining relationships between tasks in a project.
  
  Solution:
  To resolve the CN839 error, you should:
  
  Check Activity Relationships: Review the relationships you are trying to establish. Ensure that you are not linking an activity to itself.
  Modify Relationships: If you find that an activity is incorrectly set as both a predecessor and successor, modify the relationships to link it to a different activity.
  Review Activity Definitions: Ensure that the activities are defined correctly and that their relationships make logical sense within the project structure.
  Use Different Activities: If you need to create a dependency, ensure that you are using different activities for the start and target.
  
  Related Information:
  
  Transaction Codes: You may encounter this error while using transaction codes like CJ20N (Project Builder), CN21 (Create Network), or CN22 (Change Network).
  Documentation: Refer to SAP documentation or help files related to project management and network planning for more detailed guidance on activity relationships.
  SAP Notes: Check for any relevant SAP Notes that might address specific scenarios or bugs related to this error.
  
  By following these steps, you should be able to resolve the CN839 error and successfully manage your project activities in SAP.