ALR0648E The Zero Buffer Credit Rate of port port name in switch switch name was measured to be measured value cnt/s, which violated the defined critical-stress boundary value of boundary value cnt/s.
Explanation
Zero Buffer Credit Rate measures the percentage of time that the port was unable to send frames due to a lack of buffer credits at the port over a particular time interval. Buffer to Buffer Credit is used as a mechanism to enforce flow-control by the fibre channel protocol, and ensures that a transmitting port which is sending data does not overrun the ability of the receiving port to receive that data. The lack of buffer credits has a negative effect on the port's overall throughput, and can cascade from port to port causing congestion in the entire fabric. A threshold was defined on this metric, which causes the measured value to be compared to the defined boundaries for each set of performance statistics collected from the switch.
This message indicates that a threshold boundary violation occurred. In this case, the specified port in the switch has a Zero Buffer Credit Rate value that is greater than or equal to the critical-stress boundary that was defined for the related threshold.
Action
The threshold violation might indicate that a hardware or configuration problem exists either for this port or for the connected fabric. Isolated errors can be ignored in most cases, but if the rate remains consistently high over time, this may be a cause for concern. Follow the trouble-shooting guidelines for the switch, and for the connected entity (storage system, switch, or server HBA).
Because isolated temporary errors can be ignored in most cases, consider enabling the alert suppression option "Suppress alerts unless the triggering condition has been violated continuously for a specified length of time" for this threshold. This can greatly reduce the number of unnecessary alerts.