RedHat Linux OS upgradation on Oracle 11gR2 RAC environment

Two months before I was performed Linux OS upgradation on live production and test environment for one of my big client. Both environments are 2 node RAC configured.
Below mentioned steps for OS upgradation,
OS Upgrade Pre-requisites Steps:-
Kindly cross check with Oracle and RedHat for license certification matrix
Take fullbackup of OS and Database.
OS Upgrade Steps:-
(1) Shutdown DB, DBconsole (if any), Cluster, ASMlib (if any in Linux)
As RDBMS owner id “oracle”:
$ srvctl stop database -d -o immediate #– run once in any node
$ emctl stop dbconsole #– run on all nodes
As UNIX/Linux “root”:
# /bin/crsctl stop crs #– run on all nodes
# /bin/crsctl disable crs #– run on all nodes
# /etc/init.d/oracleasm stop #– run on all nodes
# /etc/init.d/oracleasm disable #– run on all nodes
(2) Backup filesystem for GRID ORACLE_HOME & RDBMS ORACLE_HOME
(3) Upgrade RedHat OS
configure RHN (Give Rhn_register command thru root user).
You have to give Redhat login user/password and your proxy address & port.
RHN will collect your system information then will send that to redhat network.
Once RHN configured then give command like #yum update --no plugin (or yum update)
It will download latest packages from redhat repository and install automatically, final stage the OS will ask you for reboot the machine.
After reboot you can get the latest kernal (using this command check the kernal and redhat os version #uname-a, cat /etc/redhat-release)
(4) Upgrade ASMlib (Download ASM packages based on latest kernal version)
# rpm -Uvh oracleasm-support-xxx
# rpm -Uvh oracleasm-2.6.xxx
# rpm -Uvh oracleasmlib-xxx
# /etc/init.d/oracleasm enable
# /etc/init.d/oracleasm lisdisks
(5) Relink RDBMS ORACLE_HOME Binary
Note: complete full steps in one node, then proceed to next
As RDBMS owner id “oracle”:
$ /bin/relink all
(6) Relink GRID ORACLE_HOME Binary
Note: complete full steps in one node, then proceed to next
As UNIX/Linux “root”:
# cd /crs/install
# ./rootcrs.pl -unlock
As RDBMS owner id “oracle”:
$ cd /bin
$ ./relink all
As UNIX/Linux “root”:
# cd /rdbms/install
# ./rootadd_rdbms.sh
# cd /crs/install
# ./rootcrs.pl –patch
(7) Enable CRS auto-startup and start CRS on all nodes
Note: complete full steps in one node, then proceed to next
As UNIX/Linux “root”:
# /bin/crsctl start crs
# /bin/crsctl enable crs
(8) Double check if DB, instances and all resrouces are ONLINE.
As RDBMS owner id “oracle”:
$ crsctl stat res -t
Reference :: How to Check Whether Oracle Binary/Instance is RAC Enabled and Relink Oracle Binary in RAC [ID 284785.1]