Resource Groups for Oracle Listener Resources

If you are using Oracle 10g, no Oracle listener 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 listener resources?

Use the answer to this question when you perform the procedure in Registering and Configuring Oracle Listener Resources.

The resource groups depend on your configuration of Oracle listeners with Real Application Clusters database instances. For general information about possible configurations of listeners for Real Application Clusters instances, see your Oracle documentation. Example configurations are described in the subsections that follow.

One Listener for One Real Application Clusters Instance

One listener serves only one Real Application Clusters instance. The listener listens on the fixed Internet Protocol (IP) address of the node. The listener cannot fail over.

In this situation, configure the listener resource as follows:

• Configure the listener resource and the RAC server resource in the same resource group.

• Ensure that this resource group is mastered on only one node.

One Listener That Cannot Fail Over for Several Real Application Clusters Instances

One listener serves several Real Application Clusters instances on the same node. The listener uses Oracle's transparent application failover (TAF) and load balancing to distribute client connections across all Real Application Clusters instances. The listener cannot fail over.

In this situation, configure the listener resource as follows:

• Configure the listener resource in its own resource group.

• Ensure that the listener's resource group is mastered on only one node.

• Create a dependency between the listener's resource group and RAC servers' resource groups.

One Listener That Can Fail Over for Several Real Application Clusters Instances

One listener that can fail over serves several Real Application Clusters instances on the same node. When the listener fails over to another node, the listener serves several Real Application Clusters instances on the other node.

The listener uses Oracle's TAF and load balancing to distribute client connections across all Real Application Clusters instances. To ensure fast error detection and short failover times, the listener listens on an address that is represented by a LogicalHostname resource.

In this situation, configure the listener resource as follows:

• Configure the listener resource and the LogicalHostname resource in the same resource group.

• Ensure that this resource group is mastered on the nodes on which Oracle Real Application Clusters is running.

For more information, see LogicalHostname Resources for Oracle Listener Resources.

One Listener for the Entire Cluster

One listener serves all Real Application Clusters instances on all nodes. The listener listens on an address that is represented by a LogicalHostname resource. This configuration ensures that the address is plumbed very quickly on another node after a node fails.

You can use this configuration if you configure Real Application Clusters instances to use a multithreaded server (MTS). In such a configuration, the REMOTE_LISTENERS parameter in the init.ora file specifies that each dispatcher registers with the listener on a logical IP address.

All clients connect through the one listener. The listener redirects each client connection to the least busy dispatcher. The least busy dispatcher might be on a different node from the listener.

If the listener fails, the listener's fault monitor restarts the listener. If the node where the listener is running fails, the listener is restarted on a different node. In both situations the dispatchers reregister after the listener is restarted.

If you are using one listener for the entire cluster, configure the following resources in the same resource group:

• The listener resource

• The LogicalHostname resource

For more information, see LogicalHostname Resources for Oracle Listener Resources.