zVM

This operating system can be used as a hypervisor.

It operates within one LPAR itself, and it can host guests each of them having and running their own operating system,

Although those guest systems won't have their own LPAR z/VM can provide the same features as PRSM, allowing the guests to share CPU, memory, CSS (Channel SubSystem)s and OSA (Open Systems Adapter) adapters.

it is common that z/VM will be used to host Linux on IBM Z partitions.