Oracle Database Tips by Donald Burleson

Oracle10g Grid Computing with RAC
Chapter 7 - Cache Fusion and Inter Instance Coordination

Recovery Features

All resources previously mastered at the failed instance are redistributed across the remaining instances. These resources are reconstructed at their new master instance. All other resources previously mastered at surviving instances remain unaffected.

The cluster manager first detects the node and instance failure. It communicates the failure status to the GCS by way of the LMON process. At this stage, any surviving instance in the cluster initiates the recovery process.

Remember, instance recovery does not include restarting the failed instance or recovering applications that were running on that instance. Also note that, even after a node failure (and instance loss), the redo log file of the failed instance is still available to the other recovering instance, since the redo log filer is located on the shared cluster file system or shared raw partition. This is an important feature of the RAC system.

Because of past images, instance recovery is performed differently in the RAC implementation. The SMON process of a surviving instance performs recovery of the failed instance (or thread). However, note that the foreground process performs recovery in a stand-alone instance.