Class &1 (&2) contains overwritten characteristics/values

What causes this issue?

Overwritten characteristics may have a negative impact on the
performance.
In transaction CL02 (class maintenance), you have the option of
overwriting characteristics and characteristic values according to their
class; that means, you can change the value set of a characteristic
depending on the class in which the characteristic occurs.
Since this always involves additional loading and the processing of
additional source code, you should not use this option for performance
reasons.

System Response

See also note 917987.

How to fix this error?

Please check your model. Avoid overwritten characteristics/values in
large models (if applicable).

Error message extract from SAP system. Copyright SAP SE.