The HMC Web Services API is the access point for any external tools to manage the IBM Z or LinuxONE platform. It supports management of the lifecycle and configuration of various platform resources, such as partitions, CPU, memory, virtual switches, I/O adapters, and more.

The zhmcclient package encapsulates both protocols supported by the HMC Web Services API:

- REST over HTTPS for request/response-style operations driven by the client. Most of these operations complete synchronously, but some long-running tasks complete asynchronously.

- JMS (Java Messaging Services) for notifications from the HMC to the client. This is used for notification about changes in the system, or about completion of asynchronous tasks started using REST.