How to enable and disable RAC option in version 9.2.0.1 to 11.1.0.8

REASON

1.                   Sometimes for ORACLE RAC DB you need to check backup/restore on server with not linked RAC option

2.                   Restore DB to new server where RAC option is not enabled and you can get

ORA-00439: feature not enabled: Real Application Clusters

3.                   If you try DBCA with no RAC servers and cluster manager with a linked RAC option into oracle you can get

ORA-00603: ORACLE server session terminated by fatal error

ORA-27504: IPC error creating OSD context

ORA-27300: OS system dependent operation:if_not_found failed with status: 0

ORA-27301: OS failure message: Error 0

ORA-27302: failure occurred at: skgxpvaddr9

CHECK IF RAC_ON or RAC_OFF

cd $ORACLE_HOME/rdbms/lib

nm -r libknlopt.a | grep -c kcsm.o

If above command returns 0, then RAC is not linked. If it returns >= 1, then it is linked.

#spfile

alter system set cluster_database=false scope=spfile;

ENABLE RAC OPTION 

cd $ORACLE_HOME/rdbms/lib

shutdown everything

make -f ins_rdbms.mk rac_on ioracle

DISABLE RAC OPTION 

cd $ORACLE_HOME/rdbms/lib

shutdown everything

make -f ins_rdbms.mk rac_off ioracle