We are having an issue with CDT reference. We got to change the namespace of CDT

Just to complement what has been already said:

Impact Analysis inspects every single item in your applications under the Applications tab to determine what objects make reference to the selected CDT. Once CDTs are registered/created in Appian Impact Analysis will identify them as unique through their name + namespace combination; that said when you change the namespace this CDT is no longer a version of the deleted one, it's a completely new one since the identifier name + namespace is no longer the same, that makes Impact Analysis unable to think that object A referencing {old_namespace}myCDT is now supposed to make reference to {new_namespace}myCDT.

This behavior is expected since Appian cannot guess that {old_namespace}myCDT is supposed to be now a new version of {new_namespace}myCDT; there's nothing that could link those CDTs specially since the way you created the new one was by deleting the old and uploading the new one; notice how at no point there's an association when you upload a CDT with a deleted one other than the one that gets created if you keep the original name and namespace.

In summary, when updating a namespace you need to:

1. Upload the CDT with the new namespace
2. Manually update your models/objects to point to the new CDT
3. Only at this point you can delete the CDT with the old namespace.

Just to complement what has been already said:

Impact Analysis inspects every single item in your applications under the Applications tab to determine what objects make reference to the selected CDT. Once CDTs are registered/created in Appian Impact Analysis will identify them as unique through their name + namespace combination; that said when you change the namespace this CDT is no longer a version of the deleted one, it's a completely new one since the identifier name + namespace is no longer the same, that makes Impact Analysis unable to think that object A referencing {old_namespace}myCDT is now supposed to make reference to {new_namespace}myCDT.

This behavior is expected since Appian cannot guess that {old_namespace}myCDT is supposed to be now a new version of {new_namespace}myCDT; there's nothing that could link those CDTs specially since the way you created the new one was by deleting the old and uploading the new one; notice how at no point there's an association when you upload a CDT with a deleted one other than the one that gets created if you keep the original name and namespace.

In summary, when updating a namespace you need to:

1. Upload the CDT with the new namespace
2. Manually update your models/objects to point to the new CDT
3. Only at this point you can delete the CDT with the old namespace.