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Migration to RAC Databases

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%.

In this section, we discuss the procedure to migrate from a standalone non-RAC database to a RAC database with multiple instances. There are many special requirements to migrate the current non-RAC database to a RAC database. We will examine these requirements and also discuss the appropriate environmental changes.

When is RAC Not a Migration Option?

Conversion to RAC may not benefit the system if:

* A supported configuration of a cluster file system or shared disks is not in use.  This can be determined via the MOSC site.

* The application was specifically designed to not use cluster database processing.  For example, if it was designed to always use a majority of data for all users.

What Will Be Covered in this Chapter?

Various combinations like migrating from a lower version of Oracle to Oracle 10g and then to a RAC environment will be covered.  In addition, in place migration where existing standalone Oracle Database 10g infrastructure is upgraded to a certified cluster environment will be included as has creating a new cluster environment and moving the data while converting from HA cluster environment to a RAC parallel database environment.

RAC Migration Overview

With the advances in RAC technology in Oracle 10g RAC cluster databases utilizing Grid technology, there is increased interest among many Oracle database customers in using the new features and converting their existing Oracle database to an Oracle RAC database.  The current standalone database may be in one of any number of conditions.  For example, the database may be in 10g stand-alone, it may be in the 9i version, or it might even still be in lower releases. At the same time, the server environment may not be from the Oracle certified hardware list. Based on these various factors, the DBA needs to develop an appropriate migration plan.

From an application point of view, there may be certain additional requirements and modifications needed to access the RAC database. Once the database is migrated to a RAC database, the client applications can either use load balancing via Oracle*Net configurations or access a specific database instance of the RAC database.  In case of packaged applications that with this upgrade will just begin accessing the RAC database, appropriate configuration changes have to be performed. For example, in the Oracle eBusiness suite, cookies have to be set up in order to use RAC. In the SAP infrastructure, it may be necessary to replace the SAP software library, dboraslib,,? with the latest RAC supported version.

Migration Methodology

There are many types of migration paths. Figure 15.1 shows the two main paths.

Figure 15.1: Main procedures to migrate to Oracle Database 10g RAC

The first procedure involves the use of the existing hardware infrastructure. To use existing hardware, additional servers nodes would be added to the environment and form the cluster. Obviously the availability of Shared Storage is an important piece of the RAC architecture, since without it utilization of RAC is not possible.


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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