Sun Cluster 3.1 10/03 Data Services Developer's Guide

Implementing a Failover Resource

A failover resource group contains network addresses such as the built in resource types logical hostname and shared address, 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.

Set the boolean resource type property Failover 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. This property defaults to 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 allows 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 and 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 (logical hostname and shared address) within the group. This means that the non-network address (data service) resources in the group will not have their Start methods called until the network addresses in the group are configured up. The Implicit_network_dependencies property defaults to TRUE.