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Migration Overview

This chapter provides an overview of the major steps required to migrate a pre-version 8 database to version 8.

These migration procedures transform an existing pre-version 8 database system (including associated applications) into a version 8 database system. Version 8 is compatible with all earlier Oracle versions and releases. Therefore, databases transformed using the migration procedures described in this book can work in the same manner as in earlier versions and, optionally, can leverage new version 8 functionality.

Several preparatory steps are required before you migrate the current production database. After migrating a database, you should perform several additional test steps to test the migration. Other procedures enable you to add new version 8 functionality to existing pre-version 8 applications.

The following topics are covered in this chapter:

• Terminology
• Overview of Migration Steps
• Role of the Database Administrator During Migration
• Role of the Application Developer During Migration

Terminology

The following terms are used throughout this document:

Migration is the process of transforming an installed version of an Oracle database into a later version. For example, transforming a version 7 database into version 8 is migrating the database system.

Upgrading is the process of transforming an installed version of an Oracle database from an installed release into a later release of the same version. For example, transforming release 8.0.3 into release 8.0.4 is upgrading.

Downgrading is the process of transforming an installed version of an Oracle database from a later release back into an earlier release. For example, transforming an Oracle database from release 8.0.4 back into release 8.0.3 is downgrading, and transforming an Oracle database from version 8 back into version 7 is downgrading.

See Also: Chapter 8, "Upgrading and Downgrading" for information about upgrading or downgrading.

The source database is the database to be migrated to version 8; typically, the source database uses an older version of Oracle software. The target database is the database into which you are migrating the source database; typically, the target database uses new version 8 software.

Overview of Migration Steps

Before you perform a database migration, you should understand the major steps in the migration process. These major steps apply to all operating systems, with the possible exception of a few platform-specific details identified in your Installation Guide.

Careful planning and use of version 8 tools can ease the process of migrating a database to version 8. The Migration Utility is the easiest way to migrate an entire database, while Export/Import and SQL copy utilities enable piecemeal migration of parts of a database.

The migration process includes the following major steps:

• Step 1: Prepare to Migrate
• Step 2: Test the Migration Process
• Step 3: Test the Migrated Test Database
• Step 4: Prepare and Preserve the Source Database
• Step 5: Migrate the Production Database
• Step 6: Tune and Adjust the New Version 8 Production Database

The following sections contain a brief outline of these steps. The purpose of these descriptions is to familiarize you with the major steps in the migration process. For detailed instructions, refer to the appropriate sections later in this book.

Step 1: Prepare to Migrate

• Become familiar with the features of the version 8 database. See Getting to Know Oracle8 and the Oracle8 Enterprise Edition for an overview of these features.
• Estimate and secure the system resources required for the migration.
• Decide which migration method to use, based on considerations involving the current production database, your migration objectives, and the behavior and capabilities of available migration methodologies.
• Develop a plan for testing the migration with a version 8 test database and a plan for testing the migrated version 8 production database.
• Prepare a backup strategy so that you can recover quickly from any unexpected problems or delays.

Step 2: Test the Migration Process

• Perform a test migration using a version 7 test database. The test migration should be conducted in an environment created for migration testing and should not interfere with the actual version 7 production database.

Step 3: Test the Migrated Test Database

• Perform the tests you planned in Step 1 on the pre-migration version 7 test database and on the version 7 test database that was migrated to version 8.
• Compare results, noting anomalies between test results on the pre-migration version 7 test database and on the version 7 test database that was migrated to version 8.
• Investigate ways to correct any anomalies you find and then implement the corrections.
• Repeat Step 1, Step 2, and the first parts of Step 3, as necessary, until the migration is completely successful and works with any required applications.

Chapter 2, "Preparing to Migrate", provides detailed information about Steps 1 through 3.

Step 4: Prepare and Preserve the Source Database

• Prepare the current production database as appropriate to ensure that its migration to version 8 will be successful.
• Schedule the downtime required for backing up and migrating the
  pre-version 8 production database to version 8.
• Perform a full backup of the current production database. This step is required only if the Migration Utility is used for the migration.

Step 5: Migrate the Production Database

• Migrate the pre-version 8 production database to version 8.
• After the migration, perform a full backup of the production database.

Chapter 3 describes Steps 4 and 5 using the Migration Utility; Chapter 4 describes Steps 4 and 5 using Export/Import. Chapter 5 describes the backup procedure after the migration.

See Also: Oracle8 Replication, Appendix B, "Migration and Compatibility", if you are migrating a pre-version 8 database system that has Advanced Replication installed.

Step 6: Tune and Adjust the New Version 8 Production Database

• Tune the new version 8 production database. The version 8 production database should perform as good as, or better than, the pre-migration Oracle database. Chapter 5 describes these tuning adjustments.
• Determine which new features of the version 8 database are appropriate to use with your data and update your applications accordingly.
• Develop new database administration procedures as needed.
• Do not migrate production users to the version 8 database until all applications have been tested and operate properly. Chapter 6 describes considerations for updating applications.

Role of the Database Administrator During Migration

Typically, the database administrator (DBA) is responsible for ensuring the success of the migration process. The DBA is usually involved in each step of the process, except for steps that involve testing applications on the migrated database.

The specific DBA duties typically include:

• meeting with everyone involved in the migration process and clearly defining their roles during migration
• performing test migrations
• scheduling the test and production migration process
• performing backups of the pre-migration version 7 production database
• completing the production database migration
• performing backups of the newly migrated version 8 production database

Users should not have access to the migrated version 8 database until after all applications have been tested and operate properly.

Role of the Application Developer During Migration

The application developer is responsible for ensuring that applications designed for the pre-migration version 7 database work correctly with the migrated version 8 database. Application developers often test applications against the migrated version 8 database and decide which available new features of version 8 should be used.

Before migrating the version 7 production database, the DBA or application developer should install a version 8 test database. Then, the application developer tests and modifies the applications, if necessary, until they work with their original (or enhanced version 8) functionality.

The following references provide information about identifying differences in the migrated version 8 database that could affect particular applications. Application developers can use these differences to guide modifications to existing applications.

• Chapter 6, "Upgrading Version 7 Applications", describes the changes required to enable existing applications (that access a version 7 database) to access a version 8 database and provides guidance for upgrading version 7 applications to take advantage of version 8 functionality.
• Getting to Know Oracle8 and the Oracle8 Enterprise Edition describes enhancements in version 8.
• Appendix B lists changed data dictionary views that an application might require and SQL reserved and key words for version 8.
• Oracle8 Parallel Server Concepts and Administration and Oracle8 SQL Reference contain descriptions of changes and new version 8 functionality.
• For a pre-version 8 database system that has Advanced Replication installed, you must also refer to Oracle8 Replication, Appendix B, "Migration and Compatibility".

Version 8 provides features that aid in upgrading existing applications to version 8:

• Net8 and SQL*Net V2 support communication between Oracle versions.
• The programming interface is unchanged between Oracle versions.
• Oracle's backward compatibility accommodates small incompatibilities between different versions and releases.

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