Using Serviceguard Extension for RAC, 9th Edition, September 2010

CRS manages Oracle's cluster resources based on configuration—including start, stop, and
monitor, and failover of the resources.
EVM publishes events generated by CRS and may run scripts when certain events occur.
When installed on a SGeRAC cluster, both the Oracle Cluster Software and RAC can continue
to rely on the shared storage capability, networking monitoring, as well as other capabilities
provided through Serviceguard and SGeRAC.
Oracle 10g/11gR1/11gR2 RAC uses the following two subnets for cluster communication purposes:
• CSS Heartbeat Network (CSS-HB): Oracle Clusterware running on the various nodes of the
cluster communicate among themselves using this network.
• RAC Cluster Interconnect Network (RAC-IC): Database instances of a database use this
network to communicate among themselves.
NOTE: In this document, the generic terms CRS and Oracle Clusterware will subsequently be
referred to as Oracle Cluster Software. The use of the term CRS will still be used when referring
to a sub-component of Oracle Cluster Software.
For more detailed information on Oracle 10g/11gR1/11gR2 RAC, refer to Chapter 2: “Serviceguard
Configuration for Oracle 10g, 11gR1, or 11gR2 RAC”.
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/11gR1/11gR2 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).
Overview of SGeRAC Cluster Interconnect Subnet Monitoring 19