The documentation contains e.g. the Technical Operations Manual in which different monitoring options are explained (e.g. alerts and the statistics server system views).
Beyond that, SAP Solution Manager provides integration for SAP HANA covering monitoring, health checks and analysis.
Reading the documentation on help.sap.com would have provided these information to you and your clients.
There's plenty of more information available, but giving the lead you just received, I'm optimistic you'll find more yourself using your search engine of trust.
- Lars
