How are events received from a Distributed Correlation Server processed by RM Event Server?
If raw sensor events are sent to a Distributed Correlation Server first, then the First-level correlation happens at the Distributed Correlation Server. After doing first level correlation, the DC Server creates Incident events and also sets the following attributes for each raw sensor event:
rm_CorrelatedByAgent = <hostname or IP of the DC server>
rm_AgentNormalized = true
Now, even if these raw sensor events are forwarded to the RM Agent on the Event Server, the Agent will know that these events have already been correlated by the DC Server. Hence it will simply pass on these events to TEC without any further correlation.
As far as Incident events generated by DC Server are concerned, the RM Agent on Event Server will not process Incident events. It simply sends it to the "Incident_Sender" which passes these events to TEC.
So, first-level correlation is always done by the first RM Agent that runs a correlation engine. It is either a DC Server or an Event Server.