Customer wants analysis of one domain and we are not sure which import to ask for

They can give us RSE, a CoreIQ catalog, or a zip of source. Which one should I ask for first?

Ask for the source they already trust. Live z/OS source comes from RSE or JZOS, IBM i libraries from JT400, and a CoreIQ or planner catalog when that is already curated. A file upload is fine when they cannot open the host to us. We do not need every option. One complete import of the domain is enough to start operations and lineage.