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| Oracle Solaris Cluster Data Services Developer's Guide Oracle Solaris Cluster 4.1

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## Implementing a Failover Resource

A failover resource group contains network addresses, such as the built-in resource types `LogicalHostname` and `SharedAddress`, and failover resources, such as the data service application resources for a failover data service. The network address resources, along with their dependent data service resources, move between cluster nodes when data services fail over or are switched over. The RGM provides a number of properties that support implementation of a failover resource.

In a global cluster, a failover resource group can fail over to a node on another Oracle Solaris host or on the same Oracle Solaris host. A failover resource group cannot fail over in this way in a zone cluster. However, if the host fails, the failing over of this resource group to a node on the same host does not provide high availability. Nonetheless, you might find this failing over of a resource group to a node on the same host useful in testing or prototyping.

Set the Boolean `Failover` resource type property to `TRUE` to restrict the resource from being configured in a resource group that can be online on more than one node at a time. The default for this property is `FALSE`, so you must declare it as `TRUE` in the RTR file for a failover resource.

The `Scalable` resource property determines if the resource uses the cluster shared address facility. For a failover resource, set `Scalable` to `FALSE` because a failover resource does not use shared addresses.

The `RG_mode` resource group property enables the cluster administrator to identify a resource group as failover or scalable. If `RG_mode` is `FAILOVER`, the RGM sets the `Maximum_primaries` property of the group to 1. The RGM also restricts the resource group to being mastered by a single node. The RGM does not allow a resource whose `Failover` property is `TRUE` to be created in a resource group whose `RG_mode` is `SCALABLE`.

The `Implicit_network_dependencies` resource group property specifies that the RGM should enforce implicit strong dependencies of non-network address resources on all network address resources (`LogicalHostname` and `SharedAddress`) within the group. As a result, the `Start` methods of the non-network address (data service) resources in the group are not called until the network addresses in the group are configured to go up. The `Implicit_network_dependencies` property defaults to `TRUE`.

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