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The RAC System

Oracle RAC Cluster Tips by Burleson Consulting

This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters.  To get immediate access to the code depot of working RAC scripts, buy it directly from the publisher and save more than 30%.

The RAC system consists of multiple nodes accessing a single database. Typically, this architecture includes multiple servers or hosts connected by a private high bandwidth and low latency interconnect.

Installation and configuration of the RAC system on multiple nodes involves many steps. Unlike a stand-alone Oracle database installation, a RAC installation is highly integrated with the cluster environment at the server level. The RAC database software installation process is cluster aware; in other words, the Oracle software detects the existence of the cluster infrastructure as it begins to install.

Installation Components

From the point of view of the installation, the main architecture of the RAC environment includes the following:

* Nodes or Servers

* Private Interconnect

* Vendor Supplied Cluster Manager or Cluster Software (Optional)

* Oracle provided Cluster Ready Services

* Shared Storage Subsystem

* Raw Partitions or Cluster File System or Network Attached Storage (NAS) or Automatic Storage Management (ASM)

* Public Network Connection

* Oracle Database software with RAC option

Nodes or Hosts

The nodes or servers are the main platforms on which the Oracle RAC database is installed. The Cluster nodes range from a high-end powerful Sun Fire 15K to a low-end Linux server. They can also range from a mainframe grade IBM zSeries server to the emerging blade-server technologies such as IBM BladeCenter or Egenera. First, the appropriate operating system needs to be installed on the nodes. It is also important to choose the appropriate number of nodes while setting up the node operating environment.

Private Interconnect

The private interconnect is the physical construct that allows inter-node communication. It can be a simple crossover cable with UDP or it can be a proprietary interconnect with specialized proprietary communications protocol. When setting up more than 2- nodes, a switch is usually needed. This provides the maximum performance for RAC, which relies on inter-process communication between the instances for cache-fusion implementation.


Creating clusters involves installation of the cluster software on all nodes in the proposed cluster, as well as checking the configuration. The necessary tests need to be performed to verify the validity of the cluster. At the same time, the necessary software that controls the private interconnect is also installed and configured. With the availability of Oracle provided Cluster Ready Services (CRS), one can achieve a uniform and standard cluster platform. CRS is more than just cluster software, but it extends the high availability services in the cluster.

Shared Storage

The storage system provides an external common disk system accessible by all nodes of the cluster. The connection from the nodes to the disk sub-system is usually through a fiber switch or a SCSI connection. Once the storage volumes are presented to the hosts in the cluster, usually with the help of the logical volume manager, one can create volumes of suitable size for use in the RAC database. With the introduction of ASM methodology, the shared storage structures can be managed very easily. Once the disk groups are created with input of the disk devices, the ASM instances on each of the node in the cluster provide the shared storage resources to create the Database Files. The preparation of storage structures has been covered extensively in Chapter 5, Preparing Shared Storage.

Public Network

The clustered servers or hosts need to have public network connectivity so that client machines in the network can access the resources on the RAC system.

Virtual IP Address for CRS

Oracle 10g release supports the concept of Service, which can be assigned the Virtual IP address, and which float among the specified nodes. By creating the Virtual IP address and Virtual Host names, the applications get a sense of transparency in their connection to the RAC database service. This will be examined further in later sections of this chapter.


This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters, Rampant TechPress, by Mike Ault and Madhu Tumma.

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.


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