Key fields of table/view &1 cannot be included

What causes this issue?

At least one field of the key of table/view &V1& cannot be put in the
BC Set.
Forbidden key fields can be for example:
Address fields (field with domains of type 'ADRNR', 'CADRNR' and
'AD_ADDRNUM')
GUID: GUIDs are unique (generated) values which should have no
significance in the customizing environment
(GUIDs are only forbidden for views and tables with generated
maintenance dialogs. Tables without generated maintenance dialog can be
put in BC Sets)
Field of type 'STRING' or 'RAWSTRING'
Field more than 255 characters wide

System Response

The table/view is not put in the BC Set.

How to fix this error?

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.