Primary subobject will not be considered for Object Types V, C, and T

What causes this issue?

Primary Subobjects are considered only for Text tables and Logical
Transports in OBJS table in which field PRIM_Table is marked as 'X'.

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.