Where do the images reside for an air-gapped Cloud Pak for Business Automation upgrade?

When performing an air-gapped upgrade of Cloud Pak for Business Automation, the images used for the upgrade reside in a local registry. An air-gapped environment is one in which there is no external network access, so the images cannot be pulled from a remote registry such as IBM registry, RedHat quay.io registry, or Docker Hub. Instead, the images must be pre-pulled and stored in a local registry that is accessible to the OpenShift cluster.