U can download Oracle from http://www.oracle.com/technology/software/products/database/oracle11g/111060_linuxsoft.html and make sure java is running before proceed.
1. create users and groups required
groupadd oinstall
groupadd dba
groupadd nobody
useradd -g oinstall -G dba,nobody -d /opt/oracle -m -s /bin/bash oracle
2. set the oracle user password
user name=oracle
passwd=oracle
3. Tune the following kernel parameters
/etc/sysctl.conf
kernel.shmall = 2097152
kernel.shmmax = 2147483648
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128
net.core.rmem_default = 262144
net.core.rmem_max = 262144
net.core.wmem_default = 262144
net.core.wmem_max = 262144
fs.file-max = 65536
net.ipv4.ip_local_port_range = 1024 65000
/etc/security/limits.conf
* soft nproc 2047
* hard nproc 16384
* soft nofile 1024
* hard nofile 65536
