Multiple classification not allowed

What causes this issue?

You want to allocate an object to more than one class. However, the
<DS:GLOS.class_type>class type</> you are using does not allow
<DS:GLOS.multiple_classification>multiple classification</>.
The class type controls whether or not an object can be allocated to
more than one class. You define class types and their features in the
IMG for <ZH>Classification</>.

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?

Check the settings for the class type in the IMG. If you require
multiple classification for this class type, ask the person responsible
for Customizing to make the required settings.

Error message extract from SAP system. Copyright SAP SE.