Actions that cluster administrators perform on resources include setting and changing resource properties. The API defines the Validate and Update callback methods so that you can create code that hooks into these administrative actions.
The RGM calls the optional Validate method when a resource is created and when a cluster administrator updates the properties of the resource or its containing group. The RGM passes the property values for the resource and its resource group to the Validate method. The RGM calls Validate on the set of cluster nodes that is indicated by the Init_nodes property of the resource's type. See Resource Type Properties or the rt_properties(5) man page for information about Init_nodes. The RGM calls Validate before the creation or the update is applied. A failure exit code from the method on any node causes the creation or the update to fail.
The RGM calls Validate only when the cluster administrator changes resource or group properties, not when the RGM sets properties, or when a monitor sets the Status and Status_msg resource properties.
The RGM calls the optional Update method to notify a running resource that properties have been changed. The RGM runs Update after the cluster administrator succeeds in setting properties of a resource or its group. The RGM calls this method on nodes where the resource is online. This method can use the API access functions to read property values that might affect an active resource and adjust the running resource accordingly.