N3T_TCP_Conn_Drop
A number of connections for a TCPIP stack were dropped because
of one or more of the following error conditions:
- Retransmit_dropped: Connections were lost
because the retransmit conditional value was exceeded.
- Probe_dropped: No response was received
while sending window probe requests.
- Alive_dropped: No response was received
while sending keepalive probe requests.
- Tcp_wait_drops: FINWAIT2 timer expiring
before receiving the FIN segment.
The TCP/IP dropped connections value is a stack aggregate metric
collected for each TCP/IP stack instance. Connections were probably
dropped because of network congestion or lost connectivity to the
endpoint node.
To monitor the connections dropped because of error conditions,
the following metrics are used:
- z/OS TCP stack layer and availability
- Response view table
- Connections dropped
This situation occurs when the number of connections dropped, because
of error conditions, is greater than zero (0) for three consecutive
intervals. To resolve this problem, use the following steps:
- Analyze the individual TCP/IP connections for the stack to determine
if there is a pattern based on subnet, or other logical grouping,
where the dropped connections are occurring.
- Issue a trace route command to determine the most probable routing
path and if connectivity to the endpoint node has been lost.
- 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. Probe_dropped and
tcp_wait_drops errors might indicate trouble with endpoint application.
Formula: TCP Connections Dropped > 0