Using Serviceguard Extension for RAC, 6th Edition, April 2008

The following describes the characteristics of subnets that can be monitored by using
the CLUSTER_INTERCONNECT_SUBNETparameter:
• A subnet used only for the communications among instances of an application
configured as a multi-node package.
• A subnet whose health does not matter if there is only one instance of an application
(package) running in the cluster. The instance is able to provide services to its
clients regardless of whether the subnet is “up” or “down” on the node where the
only instance of the package is running.
A failure of the cluster interconnect subnet on all nodes of the cluster, where the
multi-node package is running, is handled by bringing down all but one instance of
the multi-node package.
In certain 10g RAC configurations, this parameter can be used to monitor Oracle Cluster
Synchronization Services (CSS-HB) and/or RAC cluster interconnect subnet when
Oracle Clusterware and RAC Database instances are configured as Serviceguard
multi-node packages.
Cluster Interconnect Subnet Monitoring provides the following benefits:
• Better availability by detecting and resolving RAC-IC subnet failures quickly in
certain configurations. (For example, in configurations where Oracle CSS-HB
subnet and the RAC-IC subnet are not the same. This configuration helps avoid
one RAC database (RAC-IC) traffic from interfering with another.)
• Assists in providing services (on one node) when Oracle CSS-HB/RAC-IC subnet
fails on all nodes.
• Facilitates fast and reliable reconfiguration with use of multiple SG-HB networks.
• 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:
Overview of SGeRAC Cluster Interconnect Subnet Monitoring 27