Many of PC dashboards are showing no data to display ,after re-discovering the reports starts populating .What it is happening one or two devices is fine ,bulk how it is possible for all devices .
What version of CA PM are you using? The reason I am asking is that there was a bug relating to the poller configuration (PCC) that caused some metric families to drop out of the PCC and it stops effectively collecting data. This was resolved in 3.6 I believe.
As far as rediscovering in bulk, there is no "entire environment" option like there was in eHealth. If you want to rediscover everything you would need to set up a discover profile to do so.
Using 3.6 version only .
Any specific patch version ?