Requirements to check before install Oracle RAC

1)Checking the Hardware Requirements
•Physical memory: At least 1GB RAM.

•Swap space: If RAM is between 1 GB and 2 GB then make swap space to 1.5 times of the size of RAM.
If RMAN is more than 2GB then make swap space to the equal of the size of the RAM.

•Temporary space: At least 400 MB. Typically in /tmp directory.

•Processor type (CPU): Need to be certified with the version of the Oracle software being installed.

•Hard Disk Space: 1.5 GB for oracle database home directory+1.5GB for the ASM home directory+120 oracle clusterware software installation+Two Oracle Clusterware components OCR 256 MB each, or 512 MB total disk space+Three Oracle Clusterware components Voting Disk 256 MB each, or 768 MB total disk space.

•All the nodes in the cluster must have same hardware architecture. However can have machines of different speeds and size in the same cluster.

On *nix system you can check hardware components as follows.

•To determine physical RAM size, # grep MemTotal /proc/meminfo

•To determine the configured swap space, # grep SwapTotal /proc/meminfo

•To determine the amount of disk space available in the /tmp directory, # df -k /tmp

•To determine free disk space on the system, #df -h or #df -k

•To determine whether the system architecture, # grep "model name" /proc/cpuinfo

Checking the Network Requirements
Network Hardware Requirements
•One private interconnect is needed for Oracle Custerware for the use to synchronize each instance's use of the shared resources and for Oracle RAC to interconnect to transmit data blocks that are shared between the instances. Thus each node need at least two network interface cards, or network adapters. One adapter is for the public network and the other adapter is for the private network

•The public interface names associated with the network adapters for each network must be the same on all nodes, and the private interface names associated with the network adaptors should be the same on all nodes. For example if in server1/node1, eth0 is the public interface then on server2/node2 eth0 must be the public interface.

•For the public network, each network adapter must support TCP/IP.

•For the private network, the interconnect must support the user datagram protocol (UDP) using high-speed network adapters and switches that support TCP/IP.

•Note UDP is the default interconnect protocol for Oracle RAC, and TCP is the interconnect protocol for Oracle Clusterware.

•For the private network, the endpoints of all designated interconnect interfaces must be completely reachable on the network. All nodes must be accessible between through private network. You can check the reachability by ping command.

Network Parameter Requirements
If NFS is used for the shared storage, then you must set the values for the NFS buffer size parameters rsize and wsize to at least 16384. Oracle recommends that you use the value 32768.
You can set the value by updating the /etc/fstab file on each node with an entry similar to the following,

clusternode:/vol/DATA/oradata /home/oradata/app nfs
rw,bg,vers=3,tcp,hard,nointr,timeo=600,rsize=32768,wsize=32768,actimeo=0 1 2

IP Address Requirements
•You must have at least three IP addresses available for each node
1.An IP address for the public interface. Interface name should be the name of the node name.
2.An IP address for the private interface. Interface name should be hostname-priv.
3.One virtual IP address with an associated network name. Interface name should be hostname-vip.

•The VIP is on the same subnet as your public interface and it address will be not used currently in the network.

•For public and virtual addresses register with an associated network name in DNS. If you do not have an available DNS, then record the all network names and interface names in the system hosts file, /etc/hosts.

•Identify the interface names and associated IP addresses for all network adapters by running the following command on each node:

# /sbin/ifconfig


Node Time Requirements
Ensure that each member node of the cluster is set as closely as possible to the same date and time. Oracle strongly recommends using the Network Time Protocol (NTP) feature of most operating systems for this purpose.

Verifying the Installed Operating System and Software Requirements
•To determine which distribution and version of Linux is installed, run the following command as the root user:
#cat /etc/issue

•The Linux kernel is updated to fix bugs. These kernel updates are referred to as erratum kernels or errata levels. To determine if the required errata level is installed, use the following procedure as the root user:

#uname -r