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

Introduction to Serviceguard Extension for RAC
Overview of SGeRAC Cluster Interconnect Subnet Monitoring
Chapter 1 25
Overview of SGeRAC Cluster Interconnect
Subnet Monitoring
In SGeRAC, the Cluster Interconnect Subnet Monitoring feature is used
to monitor cluster communication subnets. This feature requires the use
of a package configuration parameter known as the
CLUSTER_INTERCONNECT_SUBNET. It can be set up to monitor certain
subnets used by applications that are configured as Serviceguard
multi-node packages.
The following describes the characteristics of subnets that can be
monitored by using the CLUSTER_INTERCONNECT_SUBNET parameter:
• 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.