You must choose either absolute value thresholds or baseline thresholds that apply to all transmit or receive traffic defined in the collection. Click the Use absolute values radio button on the last screen of the Performance Manager Configuration Wizard to configure thresholds that apply directly to the statistics gathered. These statistics, as a percent of the total link capacity, are compared to the percent utilization configured for the threshold type. If the statistics exceed either configured threshold, an event is shown on the DCNM-SAN web client Events tab.
https://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/11_x/fundamentals/cisco_dcnm_fu ndamentals_guide_11/monitoring_performance.html