The Customer where I am currently working for has to sites, one site is the primary site the other site is the DR site, roles are reversed each year.
The production databases are running on 10.2.0.3 and need to be urgently upgraded to a more supported version, in our case we decided to go to 188.8.131.52 with PSU 2.
on the primary site there is a 2 node RAC with a single node local standby, on the remote site there is a 2 node physical standby RAC and a single node local standby.
Since the customer has enough disk-space and cpu horse power to host a parallel environment. so at the day of the upgrade, we just stop the old 10.2.0.3 environment and promote the logical to primary and we are running..
a picture says (hopefully) more than thousand words
More detailed config coming the next blog posts