Change Existing Hostnames in 10g RAC cluster !!!

Recently we wanted to upgrade an Oracle 10g (10.2.0.5) RAC database having ASM storage to higher version i.e. Oracle 11gR2 (11.2.0.3). While checking the prechecks for the upgradation, we noticed that the 10g RAC Cluster was configured using the hostnames having ‘_’ in their names. The private and virtual hostnames were…