The size of a host for licensing purposes (based on the amount of RAM provided by a host). The size of a host (in other words, the number of host units that a host is comprised of for consumption calculations) is based on the number of GBs of RAM available on the host server. The advantage of this approach is its simplicity; technology-specific factors are not taken into consideration (for example, the number of JVMs or the number of microservices that are hosted on a server). It doesn't matter if a host is .NET-based, Java-based, or something else. You can have 10 JVMs or 1,000 JVMs; such factors don't affect the amount of monitoring that an environment consumes. For full details, see Application and Infrastructure Monitoring (Host Units).
Represents the consumption of a host unit over a time period. 1 host unit hour equates to 1 host unit being consumed for 1 hour. A host with 16 GB of RAM (1 host unit) running for a full day consumes 24 host unit hours.