Using Serviceguard Extension for RAC Version A.11.20 - (August 2011)

When properly configured, Serviceguard Extension for RAC provides a highly available database
that continues to operate even if one hardware component fails.
Group Membership
Group membership allows multiple instances of RAC to run on each node. Related processes are
configured into groups. Groups allow processes in different instances to choose which other
processes to interact with. This allows the support of multiple databases within one RAC cluster.
A Group Membership Service (GMS) component provides a process monitoring facility to monitor
group membership status. GMS is provided by the cmgmsd daemon, which is an HP component
installed with Serviceguard Extension for RAC.
Figure 2 shows how group membership works. Nodes 1 through 4 of the cluster share the Sales
database, but only Nodes 3 and 4 share the HR database. There is one instance of RAC each on
Node 1 and Node 2, and two instances of RAC each on Node 3 and Node 4. The RAC processes
accessing the Sales database constitute one group, and the RAC processes accessing the HR
database constitute another group.
Figure 2 Group Membership Services
Using Packages in a Cluster
To make other important applications highly available (in addition to the Oracle Real Application
Cluster), you can configure your RAC cluster to use packages. Packages group applications and
services together. In the event of a service, node, or network failure, Serviceguard Extension for
RAC can automatically transfer control of all system resources in a designated package to another
node within the cluster, allowing your applications to remain available with minimal interruption.
There are failover packages, system multi-node packages, and multi-node packages:
• Failover package. The typical high-availability package is a failover package. It usually is
configured to run on several nodes in the cluster, and runs on one at a time. If a service, node,
network, or other package resource fails on the node where it is running, Serviceguard can
automatically transfer control of the package to another cluster node, allowing services to
remain available with minimal interruption.
• System multi-node packages. There are also packages that run on several cluster nodes at
once, and do not fail over. These are called system multi-node packages and multi-node
packages. As of Serviceguard Extension for RAC A.11.18, the non-failover packages that
What is a Serviceguard Extension for RAC Cluster? 13