Domain System '&1' cannot be deleted as it is assigned to Cfg. Req. '&2'

What causes this issue?

Domain System with Key '&1' is still assigned to at least one Template
Configuration Request. The name of the first assigned Template
Configuration Request found is displayed.

System Response

Domain System '&1' cannot be deleted as it is assigned to Cfg. Req. '&2'

How to fix this error?

Go to transaction SOAMANAGER and delete the above mentioned Template
Configuration Request.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.