Quote:
Originally posted by jmodic
RAC = high availability
Standby = disaster recovery
In RAC environment, in most cases all the nodes of the cluster are located in the same geographical location, usualy in the same building/room. So for example if the ceiling of that building colapses, probably all the nodes of the RAC will be damaged. So what good does it do that you had RAC? That is why it is not unusual to have a standby database on some distant location that covers you in the events of such "environmental disasters".
you could also have a local standby in case you need to do PIT recovery quickly - ergo a time delay