N3V_EE_Pct_Packets_Rexmit

EE connection percent packets retransmitted is the percentage of the HPR network layer packets retransmitted compared to the number of packets sent over this EE connection during the last sample interval. Retransmissions occur when a HPR packet is sent but is not acknowledged by the receiving host within a specified timeout period. A high percentage of packets are being retransmitted for the specified enterprise extender link. The probable cause of a high number of packets being retransmitted is network congestion or constrained CPU in the remote z/OS Communications Server address space.

To determine this, the percent of packets retransmitted metric in the EE connections table is used. This situation occurs if the value for the percent of packets retransmitted is greater than 5% for 2 consecutive intervals.

Possible procedures to isolate and correct the problem include:

• Issue a trace route command to determine the most probable routing path.
• Determine if this path is using a secondary or backup routing path. If it is, identify and fix the problem with the primary path.
• Query the routing interfaces on the routing path to determine the number of packets dropped.
• Identify the routers along the routing path with the highest numbers of packets dropped.
• Validate the router configuration parameters.
• Check the OSA adapter metrics to determine if adapter constraints (such as excessive processor utilization or discards at the receive side) exist.
• Confirm that CPU utilization is high for the remote system (that is, the receive side) z/OS Communications Server address space.
• Redistribute the z/OS Communications Server workload on the remote system (receive side) of the HPR RTP connection.

Formula: Percent of Packets Retransmitted >= 5