How To Fix CL520 - Only one class can be selected as a standard class

SAP Error Message - Details

• Message type: E = Error

• Message class: CL - Classification

• Message number: 520

• Message text: Only one class can be selected as a standard class

What causes this issue?

You have selected more than one class as
<DS:GLOS.standard_class>standard class</> for an object. This is not
allowed.

System Response

The last classes you selected are automatically deselected by the
system.

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message CL520 - Only one class can be selected as a standard class ?

  The SAP error message CL520, which states "Only one class can be selected as a standard class," typically occurs when you are trying to define or modify a class in the SAP system, particularly in the context of class hierarchies or when dealing with class types.
  Cause:
  This error arises when you attempt to assign more than one class as a "standard class" in a given context. In SAP, a standard class is a class that serves as a reference or base class for other classes. The system enforces the rule that only one class can be designated as the standard class to maintain a clear and unambiguous class hierarchy.
  Solution:
  To resolve this error, you should follow these steps:
  
  
  Check Existing Classes: Review the classes that are currently defined in the system. You can do this by navigating to the class definition in the SAP GUI (transaction code CL02 for display or CL01 for creation).
  
  
  Identify the Standard Class: Determine which class is currently set as the standard class. You can find this in the class attributes or properties.
  
  
  Modify Class Assignment:
  
  If you need to change the standard class, you must first remove the standard designation from the current class before assigning a new one.
  Ensure that only one class is marked as the standard class at any given time.
  
  
  
  Save Changes: After making the necessary adjustments, save your changes and check if the error persists.
  
  
  Consult Documentation: If you are unsure about the implications of changing the standard class, refer to SAP documentation or consult with a colleague who has experience with class hierarchies in your specific SAP environment.
  
  
  Related Information:
  
  Class Hierarchy: Understanding the class hierarchy in SAP is crucial. Classes can inherit properties and methods from their parent classes, and the standard class often serves as a base for other classes.
  SAP Notes: Check SAP Notes for any specific patches or updates related to this error message. Sometimes, there may be known issues or additional guidance provided by SAP.
  Authorization: Ensure that you have the necessary authorizations to make changes to class definitions in the SAP system.
  
  By following these steps, you should be able to resolve the CL520 error and successfully manage your class definitions in SAP.