Using Serviceguard Extension for RAC, 5th Edition, June 2007

Introduction to Serviceguard Extension for RAC
Overview of SGeRAC Cluster Interconnect Subnet Monitoring
Chapter 126
• Allows separation of SG-HB and Oracle RAC-IC traffic
(recommended when RAC-IC traffic may interfere with SG-HB
traffic).
How Cluster Interconnect Subnet Works
The CLUSTER_INTERCONNECT_SUBNET parameter works similar to the
existing SUBNET package configuration parameter. The most notable
difference is in the failure handling of the subnets monitored using these
individual parameters.
While the failure of subnets monitored using SUBNET package
configuration parameter is handled by halting the instance of the
package on the node where the subnet has failed, the failure of subnets
monitored using CLUSTER_INTERCONNECT_SUBNET package configuration
parameter is handled by ensuring at least one instance of the multi-node
package remains running in the cluster.
For example, when a multi-node package (pkgA) is configured to run on
all nodes of the cluster, and configured to monitor a subnet (SubnetA)
using the CLUSTER_INTERCONNECT_SUBNET parameter:
• If more than one instance of pkgA is running in the cluster and
SubnetA fails on one of the nodes where the instance of pkgA is
running, the failure is handled by halting the instance of pkgA on the
node where the subnet has failed.
•If pkgA is running on only one node of the cluster and SubnetA fails
on that node, pkgA will continue to run on that node after the failure.
•If pkgA runs on all nodes of the cluster and SubnetA fails on all nodes
of the cluster, the failure is handled by halting all but one instance of
pkgA. Where the instance of pkgA will be left running is randomly
determined.
The following describes the behavior of cluster interconnect subnet
monitoring feature under the following scenarios:
• For a multi-node package with CLUSTER_INTERCONNECT_SUBNET
configured, upon an explicit request to start the package on a node,
no attempt to start the package instance on that node will be made if
the subnet is not up on that node.
• If a multi-node package with CLUSTER_INTERCONNECT_SUBNET
configured is running on only one node of the cluster, with the subnet
that it monitors is down on all nodes of the cluster, the restoration of