This onboarding mode is for systems that are about to be retired and for which you only want to handle production deployments in a controlled manner, while eschewing the benefits of testability and having your DB objects in code as mentioned in the Onboarding Guide.
Onboarding to this mode is pretty simple. All you need to do is the same steps you applied in the kata example, e.g.:
Note that there is no reverse-engineering concept here; i.e. if your tables already exist in production, then do not try to also create a “CREATE TABLE” statement in your files as well, just the alters. For newly-created tables, then it is okay to add the “CREATE TABLE” statement.
If you do still seek to have your “create table” definitions in code, please look at the Onboarding Guide and see the “Existing Systems” options.