本系列文章详细记录了在已有两个rac节点的基础上，添加rac第3个节点的过程,期间对rac的使用没有任何影响，rac节点的操作系统均为

1：配置新节点操作系统环境同其他节点一致，包括共享存储，补丁包，内核参数，，用户环境变量等等
[root@rac3 ~]# cat /etc/hosts
127.0.0.1 localhost.localdomain localhost
192.168.1.41 rac1.yang.com rac1
192.168.122.41 rac1-priv.yang.com rac1-priv
192.168.1.141 rac1-vip.yang.com rac1-vip

192.168.1.42 rac2.yang.com rac2
192.168.122.42 rac2-priv.yang.com rac2-priv
192.168.1.142 rac2-vip.yang.com rac2-vip

192.168.1.43 rac3.yang.com rac3
192.168.122.43 rac3-priv.yang.com rac3-priv
192.168.1.143 rac3-vip.yang.com rac3-vip

[root@rac3 ~]# getenforce
Disabled
[root@rac3 ~]# groupadd oinstall
[root@rac3 ~]# groupadd dba
[root@rac3 ~]# useradd -g oinstall -G dba Oracle
[root@rac3 ~]# echo 'oracle' |passwd --stdin oracle
Changing password for user oracle.
passwd: all authentication tokens updated successfully.

[root@rac3 ~]# tail /etc/sysctl.conf
kernel.shmall = 2097152
kernel.shmmax = 21474838
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128
fs.file-max = 65536
net.ipv4.ip_local_port_range = 1024 65000
net.core.rmem_default = 262144
net.core.rmem_max = 262144
net.core.wmem_default = 262144
net.core.wmem_max = 262144
[root@rac3 ~]# sysctl -p

[root@rac3 ~]# tail -4 /etc/security/limits.conf
oracle soft nproc 2047
oracle hard nproc 16384
oracle soft nofile 1024
oracle hard nofile 65536

[root@rac3 ~]# tail -1 /etc/pam.d/login
session required pam_limits.so

[root@rac3 ~]# tail -1 /etc/modprobe.conf
options hangcheck-timer hangcheck_tick=30 hangcheck_margin=180

[root@rac3 ~]# modprobe -v hangcheck-timer
insmod /lib/modules/2.6.9-.EL/kernel/drivers/char/hangcheck-timer.ko hangcheck_tick=30 hangcheck_margin=180

2：在新节点上配置共享存储，创建相关目录，设置用户环境变量
[root@rac3 ~]# chown -R oracle.oinstall /u01/
[root@rac3 ~]# su - oracle
[oracle@rac3 ~]$ cat .bash_profile
# .bash_profile
# Get the aliases and functions
if [ -f ~/.bashrc ]; then
. ~/.bashrc
fi

PATH=/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin:/root/bin
export EDITOR=vim
export ORACLE_SID=racdb3
export ORACLE_BASE=/u01/app/oracle
export ORACLE_HOME=$ORACLE_BASE/product/10.2.0/db_1
export ORA_CRS_HOME=$ORACLE_BASE/product/10.2.0/crs_1
export LD_LIBRARY_PATH=/lib
alias sqlplus='/usr/local/rlwrap/bin/rlwrap sqlplus'
alias rman='/usr/local/rlwrap/bin/rlwrap rman'
export NLS_DATE_FORMAT='YYYY-MM-DD HH24:MI:SS'
export NLS_LANG=american_america.UTF8
export PATH=$ORACLE_HOME/bin:$ORA_CRS_HOME/bin:$PATH
umask 022
[oracle@rac3 ~]$ mkdir -p $ORACLE_BASE/admin
[oracle@rac3 ~]$ mkdir -p $ORACLE_HOME
[oracle@rac3 ~]$ mkdir -p $ORA_CRS_HOME

3：配置各个节点的ssh对等性
[oracle@rac3 ~]$ ssh-keygen -t dsa
[oracle@rac3 ~]$ ssh-keygen -t rsa
使用ssh-copy-id命令将rac3节点的公钥导入到rac1,rac2上的/home/oracle/.ssh/authorized_keys文件中，步骤不在赘述；
最终需要实现在3个节点上使用oracle用户进行相互ssh登陆不需要输入密码