A Start method should not exit with success until the underlying application is actually running and available, particularly if other data services are dependent on it. One way to verify success is to probe the application to verify it is running before exiting the Start method. For a complex application, such as a database, be certain to set the value for the Start_timeout property in the RTR file sufficiently high to allow time for the application to initialize and perform crash recovery.
Because the application resource, DNS, in the sample data service launches quickly, the sample data service does not poll to verify it is running before exiting with success.
If this method fails to start DNS and exits with failure status, the RGM checks the Failover_mode property, which determines how to react. The sample data service does not explicitly set the Failover_mode property, so this property has the default value NONE (unless the cluster administrator has overridden the default and specified a different value). In this case, the RGM takes no action other than to set the state of the data service. User intervention is required to restart on the same node or fail over to a different node.