If an application service process becomes unavailable, the Service Manager can restart the application service or fail it over to a back-up node. When the Service Manager fails over an application service, it starts the service on another node that the service is configured to run on.
The following situations describe how the Service Manager restarts or fails over an application service:
If the primary node running the service process becomes unavailable, the service fails over to a back-up node. The primary node might be unavailable if it shuts down or if the connection to the node becomes unavailable.
If the primary node running the service process is available, the domain tries to restart the process based on the restart options configured in the domain properties. If the process does not restart, the Service Manager may mark the process as failed. The service then fails over to a back-up node and starts another process. If the Service Manager marks the process as failed, the administrator must enable the process after addressing any configuration problem.
If a service process fails over to a back-up node, it does not fail back to the primary node when the node becomes available. You can disable the service process on the back-up node to cause it to fail back to the primary node.
The following image shows how you can configure primary and back-up nodes for an application service: