If you are using Oracle 10g, no Oracle RAC server resources are required. These resources are not required with Oracle 10g because Oracle CRS starts and shuts down Oracle Real Application Clusters database instances. In versions of Oracle earlier than 10g, these resources are required to enable Sun Cluster to start and shut down database instances.
Which resource groups will you use for the Oracle Real Application Clusters (RAC) server resources?
You require one resource group for each Oracle Real Application Clusters database instance. Each resource group contains the Oracle RAC server resource for the database instance.
Use the answer to this question when you perform the procedure in Registering and Configuring Oracle RAC Server Resources.