In most cases and several deployments, there are multiple collectors connecting to the same VMware vCenter(s).
Collection and publication of metrics is split between collectors; however, all events are collected from the vCenter by all collectors and are eventually presented to all VEM agents. In this scenario it is reasonable to expect duplicate alerts/messages in the Operations Manager console.
How this is resolved with MS SCOM?
When the collectors start gathering data from a VC, they will all trigger discovery. The top object will be the same for all collectors looking at the same vCenter; however, only the "instance" of the vCenter discovered by the collector that was the first to log the discovery, is used for creation of topology and alerting the vCenter events. This approach helps prevent any duplicate alerts.
The behavior of HP Open View
HPOV does not rely on the service map which is only constructed for the visual reference of the Operator. The duplicate generic VC events will not be filtered and are expected to appear in the messages list; however, nworks provides a solution for this and it is possible to disable capturing generic VC events on specific collectors.
To do this:
In the nworks UI go to "Enterprise Manager" tab and select a collector