How To Fix CN611 - Network contains loops and cannot be scheduled

SAP Error Message - Details

• Message type: E = Error

• Message class: CN - Meldungen für Netzpläne

• Message number: 611

• Message text: Network contains loops and cannot be scheduled

What causes this issue?

The network cannot be scheduled because there are relationships to
activities which create a loop.

System Response

INCLUDE 'NA_ALLG_NOFUNKTION' OBJECT DOKU ID TX

How to fix this error?

RESET N1
Call up the network structure graphic.
Select the menu options <ZH>Edit -> Functions -> Loop analysis ->
Execute</>.
The relationships which create loops are highlighted.
Choose new relationships between activities so that no loops exist.
Select the menu options <ZH>Edit -> Functions -> Loop analysis ->
Execute</>.
The relationships are no longer highlighted.

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message CN611 - Network contains loops and cannot be scheduled ?

  The SAP error message CN611 ("Network contains loops and cannot be scheduled") typically occurs in the context of project management within SAP, particularly when dealing with networks in the Project System (PS) module. This error indicates that there is a circular dependency in the network activities, which prevents the system from scheduling the project correctly.
  Cause:
  
  Circular Dependencies: The most common cause of this error is the presence of circular dependencies among activities in the network. This means that one or more activities are interlinked in such a way that they create a loop, making it impossible for the scheduling algorithm to determine a valid sequence of execution.
  Incorrect Relationships: Incorrectly defined relationships (predecessors and successors) between activities can lead to loops. For example, if Activity A is a predecessor of Activity B, and Activity B is also a predecessor of Activity A, this creates a loop.
  Multiple Paths: If there are multiple paths between activities that create a cycle, the scheduling engine will not be able to resolve the dependencies.
  
  Solution:
  
  Review Activity Relationships: Check the relationships between the activities in the network. Ensure that there are no circular dependencies. You can do this by reviewing the predecessor and successor relationships in the network.
  Adjust Dependencies: If you find any circular dependencies, adjust the relationships to eliminate the loops. This may involve changing the sequence of activities or redefining the dependencies.
  Use the Network Overview: Utilize the network overview tools in SAP to visualize the network and identify any loops. This can help you pinpoint where the circular dependencies exist.
  Recreate the Network: In some cases, if the network is complex and difficult to untangle, it may be easier to recreate the network from scratch, ensuring that the relationships are defined correctly from the beginning.
  Check for Errors in Activity Definitions: Ensure that all activities are defined correctly and that there are no missing or incorrect settings that could contribute to the issue.
  
  Related Information:
  
  Transaction Codes: You can use transaction codes like CN21 (Create Network), CN22 (Change Network), and CN41 (Network Overview) to manage and review networks.
  SAP Notes: Check SAP Notes for any known issues or patches related to network scheduling and circular dependencies.
  Documentation: Refer to the SAP documentation for Project System (PS) for best practices on defining networks and managing dependencies.
  
  By following these steps, you should be able to resolve the CN611 error and successfully schedule your project activities in SAP.