OpenVMS Cluster Systems - OpenVMS Systems - HP

Troubleshooting the NISCA Protocol
F.2 Addressing LAN Communication Problems
This message is displayed when PEDRIVER recently had to perform an
excessively high rate of packet retransmissions on the LAN path consisting
of the local device, the intervening network, and the device on the remote node.
The message indicates that the LAN path has degraded and is approaching,
or has reached, the point where reliable communications with the remote node
are no longer possible. It is likely that the virtual circuit to the remote node
will close if the losses continue. Furthermore, continued operation with high
LAN packet losses can result in significant loss in performance because of the
communication delays resulting from the packet loss detection timeouts and
packet retransmission.
The corrective steps to take are:
1. Check the local and remote LAN device error counts to see whether a problem
exists on the devices. Issue the following commands on each node:
$ SHOW DEVICE local-device-name
$ MC SCACP
SCACP> SHOW LAN device-name
$ MC LANCP
LANCP> SHOW DEVICE device-name/COUNT
2. If device error counts on the local devices are within normal bounds, contact
your network administrators to request that they diagnose the LAN path
between the devices.
F.2.4 Preliminary Network Diagnosis
If the symptoms and preliminary diagnosis indicate that you might have a
network problem, troubleshooting LAN communication failures should start
with the step-by-step procedures described in Appendix C. Appendix C helps you
diagnose and solve common Ethernet and FDDI LAN communication failures
during the following stages of OpenVMS Cluster activity:
• When a computer or a satellite fails to boot
• When a computer fails to join the OpenVMS Cluster
• During run time when startup procedures fail to complete
• When a OpenVMS Cluster hangs
The procedures in Appendix C require that you verify a number of parameters
during the diagnostic process. Because system parameter settings play a key role
in effective OpenVMS Cluster communications, Section F.2.6 describes several
system parameters that are especially important to the timing of LAN bridges,
disk failover, and channel availability.
F.2.5 Tracing Intermittent Errors
Because PEDRIVER communication is based on channels, LAN network problems
typically fall into these areas:
• Channel formation and maintenance
Channels are formed when HELLO datagram messages are received from a
remote system. A failure can occur when the HELLO datagram messages are
not received or when the channel control message contains the wrong data.
F–6 Troubleshooting the NISCA Protocol