Active table missing for relations attributes for IO class '&2' in '&1'

What causes this issue?

For the given IO class, no active table for storing attributes for
incoming relations could be identified.

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?

For the table record in which the objects of the given IO class are
stored, check in the following tables whether an active table is
specified in the field REPROPTAB:
SDOKLOPHRTAB, if this is a LOIO class
SDOKPHRTAB, if this is a PHIO class
If an active table is not specified, you can use the report
RSIR_M_COPY_TABSET to add it.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.