RFC Error: User misses authorization object S_RFCACL in backend system

What causes this issue?

In the backend system the user has no authorization that contains the
authorization object S_RFCACL.
This error is also triggered in case the logon was carried out using one
of the protected users 'DDIC' or 'SAP*'.

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?

Provide the user with the relevant authorization or do not use either of
the protected users 'DDIC' and 'SAP*'.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.