Object relationship hierarchies determine how one object is related to another. When you create alert definitions, you select the relationship to identify the symptom object with respect to the base object. These relationships, for example, ancestor or descendant, produce results based on how the objects are placed in the relationship hierarchy.
vCenter Server Relationship Hierarchies
Depending on the configuration of your vCenter Server instances, objects have the following possible hierarchies, from higher to lower objects:
Datacenter, Host, Virtual Machine, Datastore
Datacenter, Cluster, Host, Virtual Machine, Datastore
Datacenter, Host, Datastore
Datacenter, Cluster, Host, Datastore