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Migration Features

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%.

If the necessary hardware in terms of nodes, interconnect, and storage arrays, etc. is already available, the same infrastructure will be used.

9i-RAC implementation with Veritas Advance Cluster requires that the shared storage support the SCSI-3 PR. In this case, it would be important to ensure that the supporting storage array is used.

The utility vxfentsthdw can be used to verify that shared storage arrays support SCSI-3 persistent reservations and I/O fencing. The utility can be used to test one disk at a time, a set of disks specified in a file, or a disk group.

For Release 3.5 MP1 of DBE/AC for Oracle9i RAC, disk groups created on shared volumes are not automatically configured with I/O fencing enabled. To enable I/O fencing, the shared disk group must be deported and then imported.

If the current database files are using the Veritas Quick I/O feature, they should be converted to regular VxFS files before installing VERITAS DBE/AC for Oracle9i RAC, which uses the ODM (Oracle Disk Manager) interface for high performance file access.

Remove the earlier version VCS software and install patches and the new DBE/AC packages. Follow the Veritas documentation to configure the CVM, CFS, and VCS with default service groups. Start the cluster and keep it running.

Ensure that DB files are moved to the CFS based file system. Then, perform the same changes at the database level as explained in the previous section to move DB files into a RAC database.  These steps convert the single instance Oracle into a multi-node RAC database.

Packaged Applications

When the Oracle database supporting vendor supplied packaged applications is migrated or converted to a multi-node RAC database, there are specific ways these applications can utilize the features of the RAC database. With the multiple instances providing more scalability and high availability at the database level, the applications need to make use of such features. The following sections will provide a brief look at the discipline followed in an application client environment. 

In Case of SAP Applications

The server side and client side configuration changes may include:

Verification Process

Before the database files are transferred to the target system, verify that the Oracle database on the existing system is in the right condition for the upgrade. Specifically for this task, SAP provides two specific SQL scripts to perform some checks in advance of the Oracle Database 10g database upgrade. The scripts are called checks.sql and premig.sql and they can be found on the first RDBMS CD from SAP for Oracle Database 10g Release 10.1.

Upgrade SAP Software and Tools

For the correct use of transparent application failover, the SAP software library dboraslib must be replaced by a new version. This library is located in the directory /usr/sap/<SID>/exe/run together with all other executables for a specific SAP R/3 system. The new version of the library is compiled using the OCI 8 call interface to access the database, whereas the original version up to SAP R/3 4.6D was compiled and shipped using OCI 7 call semantics.

The new dboraslib must be requested from SAP directly. It is not currently part of any shipping CD set for release 4.6D. Additionally, it is not available on SAP?s service market place or through OCS.

The library must be replaced on all SAP R/3 application servers. Additional SAP R/3 application servers outside of the database cluster configuration may possibly use a different operating system.

The Oracle client software for Oracle9i must also be installed on every additional SAP R/3 application server. The Oracle software version used to build the shared library, dboraslib, and the installed Oracle client version must match.


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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