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Monday, 17 September 2012

Basic Concept: Upgradation/Migration Process

Before starting actual operation we will understand some of the basic concept related to Migration and Upgradation tools and technique in oracle database.
Upgradation:  Upgrade is the process of replacing our existing software with a newer version of the same product type. Upgrading our applications usually does not require special tools. Our existing reports should look and behave the same in both products. However, sometimes minor changes may be seen in product. Upgradation is done at Software level. For Example: Replacing Oracle 9i release to oracle 10g release, SQL Server 2005 to SQL Server 2008
Migration:   Migration is the process of replicating applications from one product type to another product type. A migration is any change that transforms our hardware and/or software architecture to a new state (process to transfer database between different OS). Migration is done as database level. For example:  Migrating data from DB2 to Oracle, Oracle to SQL server and Transforming existing Oracle 9i application to oracle 10g application.

Now It is easier to upgrade your existing Oracle Database. In the past, there were several tedious, manual processes that had to be outlined and documented, tested and proven, prior to upgrading. With Oracle Database 10g, the upgrade process is available through the Oracle 10g Enterprise Manager. All tasks, processes, and post-upgrade tasks are available after your installation of the Oracle Database 10g binaries. There is direct upgrade from 8.1.7.4, 9.0.1.4 or higher, 9.2.0.4 or higher, and 10.1.0.2 or higher to the newest Oracle Database 10g release is supported.
Look at the below figure to see what each part of release number represents.
Best of my knowledge you can Migrate/Upgrade your database through the following ways:
  1. Use Export/Import Utilities.
  2. Use the Database Upgrade Assistant (DBUA) tool to Upgrade.
  3. Manual Upgrade using SQL Scripts.
  4. Use of 'CREATE TABLE AS SQL Statement'.
  5. Use of RMAN
Unlike DBUA or a manual upgrade, the Export and Import or Oracle Data Pump utilities physically copy data from your current database to a new database. This upgrade method does not change the current database, which enables the database to remain available throughout the upgrade process.

The benefit of doing and EXPORT and IMPORT are you get to unload and reload data thus coalescing space, resetting your high water marks, and an opportunity to clean up your database and the negative side is if you have huge data it will take time through export/import.
Where as the DBUA can perform Migration/Upgration quickly and easily with its GUI wizard. When you install oracle 10g on that database server, it will detect the presence of oracle 9i and ask you, want it to be migrated to the latest version. You can also launch this tools later. It allows you to upgrade the database in place. You have to be at 9.2.0.4+ to be able to use the DBUA. It provides support for Oracle Real Application Clusters (RAC). In an Oracle RAC environment, DBUA upgrades all the database and configuration files on all nodes in the cluster.
A manual upgrade consists of running SQL scripts and utilities from a command line to upgrade a database to the new Oracle Database release. It keeps your full intention or control over the upgrade process.

If you are planning Migrate/Upgrade your database then you must read latest release guide. For example if you are going to upgrade oracle 9i to 10g then read this guide Oracle Database 10g Release 2 (10.2) Upgrade Guide before actual task performing and make a note for every important aspect and apply first it is on test environment. The release guide contains more depth information, will solve your lot of Migration/Upgration related issues. There are many new features in Oracle 10g which you might want to read about in the  Oracle Database 10g Release 2 (10.2) New Features Guide.


Oracle provides the latest updates, pre-upgrade, post upgrade compatibility on My Oracle Support: https://support.oracle.com. You are also able to find here latest information about patch set, pre-upgrade information tools and other companion.
Steps or Role of DBA during Upgrade/Migrate:
  1. Read the Upgrade/Migrate release guide and try to collect new features.
  2. Make a note for preparing Upgrade/Migrate
  3. Apply the process on Test Environment.
  4. Test the Upgraded Test database.
  5. Prepare and preserve the Production DB (Estimate the downtime requires for backup and upgrade)
  6. Upgrade/Migrate the Production DB
  7. Tune and Adjust the Production DB

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