Review this topic to understand the benefits of Export/Import data migration.

The Export/Import data migration method does not change the current database, which enables the database to remain available throughout the upgrade process. However, if a consistent snapshot of the database is required (for data integrity or other purposes), then the database must run in restricted mode or must otherwise be protected from changes during the export procedure. Because the current database can remain available, you can, for example, keep an existing production database running while the newly upgraded Oracle Database database is being built at the same time by Export/Import. During the upgrade, to maintain complete database consistency, changes to the data in the database cannot be permitted without the same changes to the data in the newly upgraded Oracle database.

Most importantly, the Export/Import operation results in a completely new database. Although the current target database ultimately contains a copy of the specified data that you migrated, the upgraded database can perform differently from the original source database. Although Export/Import creates an identical copy of the database, other factors can cause unexpected performance issues. (For example: disk placement of data, and unset tuning parameters).

Migrating data when upgrading Oracle Database using Export/Import provides benefits that can increase performance.

Using Export/Import to migrate data provides the following benefits:

• Defragments the data. You can compress the imported data to improve performance.

• Restructures the database. You can create new tablespaces or modify existing tables, tablespaces, or partitions that you want to populate with imported data.

• Facilitates side-by-side testing of the old and new releases of Oracle Database because an entirely new database is created.

• Enables the copying of specified database objects or users. Importing only the objects, users, and other items you need is useful for establishing a test environment for the new software on only a subset of the production data. Data Pump Export/Import provides flexible data-subsetting capabilities.

• Serves as a backup archive. You can use a full database export as an archive of the current database.

• Enables you to establish the upgraded database on a different operating system or hardware platform than the platform on which your earlier release database is placed.

• Network-based Data Pump Import enables you to load the new release Oracle Database directly across the network for your earlier release Oracle Database. By using network-based Data Pump import, you are not required to use intervening dump files.

Understand the time it takes for data migration using Oracle Data Pump.

Migrating an entire Oracle Database by using Oracle Data Pump using Export/Import can take a long time, especially compared to using DBUA or performing a manual upgrade. If you use Oracle Data Pump to migrate data, then schedule the migration during non-peak hours or make provisions for propagating to the new database any changes that are made to the current database during the upgrade.