Some metric family discoveries such as QoS can produce a large amount of components to be discovered, sometimes in to the millions depending on the size of your environment. This can cause performance issues such as slow dashboards, slow Data Aggregator Startup, etc.
CA Performance Management
Before applying a Monitoring Profile containing Metric Families such as QoS widely,
create a small collection of a representative sample of devices in your network
to which you can apply the Monitoring Profile to.
This way you can get an idea of what would be discovered in your network should you deploy more widely.
You can then adjust the metric families in your Monitoring Profile, filtering, etc, accordingly.
Note that filtering at the Monitoring Profile will not prevent components from being discovered.
Monitoring profile filtering will still save all the discovered components to the database, and filtered
components will just not be monitored.
If after testing you need to filter out components to reduce the number saved to the database, see:
KB000045041: Using Vendor Certification extensions to filter component element discovery
If you believe you may have already discovered a large amount of components see:
KB000045131: Too many components discovered, possibly resulting in slow system