Howdy Cristiano,
I would agree with David on this that you have several issues that need to be researched to find why you have smartstor duration above the 3.5 second level.
The clamp of 1.2 million is typically per agent and the default limit for metrics is 50,000 so if an agent is producing 24 times the metric generation, really good chance you have issues with metrics. Typically your historic metric load will vary in the re-periodization configuration you have set. Our settings are 15 seconds for 7 days, 60 seconds for 23 days (30 days) then 10 minutes for 60 days (90 days). This has worked pretty well and our historic metric count stays below 1.2.
We have worked with the application team to use more prepared statements that are ordered so that the "select a, b" where does not get called with "select b, a where". We have also worked with the mainframe cross enterprise agent admin to turn off metrics that were storing PID values as metadata which made the historic metric count grow very large over a month. There is also an SQL normalization within the Java/.NET agents to try to trim down the noise and provide actionable metrics.
There are several EM metrics that might be able to help with your research in this matter.
Enterprise Manager:
Number of Metrics
Number of Historic Metrics
Graph both over 24 hours, 7 days and 30 days and you are looking for large (50% to +100%) growth rates with the historic metrics should be in line with the number of metrics.
Agent
Metric Count
Historical Metric Count
Error Snapshot Events Per Interval
Transaction Tracing Events per Interval
The agent metrics would help you figure out which agent(s) to target, go after the agents reporting the largest metrics and work your way down.
On an agent, the error and transaction traces have quite a bit overhead. For error traces, you might want to triage the errors with the application development team and try to get the error events down. Transaction traces can be controlled within the agent configuration on the polling period. If you have a very high number of applications within your environment, you might want to increase the period between traces.
Your total collector capacity will be very dependent on your I/O channel to write/read from the physical storage and the amount of data (metric values, metric meta data (labels), transaction and error traces) is being stored within the 7.5 second data window.
Hope this helps,
Billy