Unit & cannot be deleted as used in assignment of matl & to layout mod. &

What causes this issue?

You wanted to delete the unit of measure &V1&. This is not possible
because it is still used in the assignment of material &V2& to layout
module &V3&.
<ZH>Note</>
If you are maintaining a generic material, this message is also issued
if the unit of measure is used in a material variant for assignment to
a layout module.

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?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.