Data Holder migrating between Service Providers

Question

If a Data Holder (DH) migrates from one service provider to another and changes the endpoint for a set of CDR endpoints, then what response should the DH provide for the original domain?

For example, the GET Products endpoint is migrated from http://openbanking.domainA.com.au/ to http://openbanking.domainB.com.au/ 

What is the recommended response for a call to http://openbanking.domainA.com.au/?

Answer

The response should be  HTTP 404 response indicating the service can no longer be found. This is industry best practice, according to the definitions of HTTP error codes.

The standards do not specifically mandate the response, hence there is no issue of non-compliance.