CA Performance Center web console > System health > Data Aggregator Polling, Polled Item count and Calculated Metrics Per Second views are showing any data
1) Make sure the /etc/host files on Data Collector contains correct IP information for the Data Collector
2) Restart the data collector:
service dcmd stop
service activemq stop
service dcmd start
Note that starting dcmd starts activemq as well so no start command for activemq is required.