How To Fix MC018 - No cyclic foreign keys possible

SAP Error Message - Details

• Message type: E = Error

• Message class: MC - Aggregate: views, matchcodes, lock objects

• Message number: 018

• Message text: No cyclic foreign keys possible

What causes this issue?

An aggregate (matchcode object, view, lock object) comprises several
tables which are connected with foreign keys. A primary table is
assumed to which further secondary tables can be added if they are
connected to the primary table with foreign key relationships. There
may be only one path with regard to the foreign key from the primary
table to each of the secondary tables.

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?

Please check the foreign key relationships of the tables embraced by
the aggregate. If necessary, you must delete one of the secondary
tables or its foreign key so that the path from the
primary to the secondary tables is unambiguous.

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message MC018 - No cyclic foreign keys possible ?

  The SAP error message MC018 "No cyclic foreign keys possible" typically occurs in the context of data modeling or when working with InfoObjects in SAP BW (Business Warehouse). This error indicates that there is an attempt to create a cyclic relationship between InfoObjects, which is not allowed in the data model.
  Cause:
  The error arises when you try to define foreign keys in a way that creates a cycle. For example, if you have three tables (or InfoObjects) A, B, and C, and you define foreign keys such that:
  
  A references B
  B references C
  C references A
  
  This creates a cyclic dependency, which can lead to ambiguity in data retrieval and integrity issues.
  Solution:
  To resolve the MC018 error, you need to review the relationships between your InfoObjects and ensure that there are no cyclic foreign keys. Here are steps you can take:
  
  
  Review Foreign Key Relationships: Check the foreign key definitions in your InfoObjects. Ensure that they do not create a cycle. You may need to remove or redefine some relationships.
  
  
  Redesign Data Model: If your data model inherently requires cyclic relationships, consider redesigning it. You might need to introduce additional InfoObjects or change the way data is structured to avoid cycles.
  
  
  Use Hierarchies: If applicable, consider using hierarchies instead of direct foreign key relationships. Hierarchies can help represent relationships without creating cycles.
  
  
  Consult Documentation: Refer to SAP documentation or guides related to InfoObject modeling and foreign key relationships for best practices and examples.
  
  
  Testing: After making changes, test the data model to ensure that it functions correctly and that the error no longer appears.
  
  
  Related Information:
  
  SAP BW Modeling: Understanding how InfoObjects, DataStore Objects (DSOs), and InfoCubes work together can help prevent such errors.
  Data Integrity: Maintaining data integrity is crucial in data warehousing, and avoiding cyclic foreign keys is part of ensuring that.
  SAP Notes: Check SAP Notes for any specific patches or updates related to this error message, as there may be known issues or fixes provided by SAP.
  
  If you continue to face issues, consider reaching out to your SAP support team or consulting with an SAP BW expert for further assistance.