When moving an Oracle database from on-premises to the AWS Cloud, there are essentially two options: moving off of Oracle (heterogeneous migration) or staying on Oracle (homogeneous migration). You don’t alter the database engine during a homogenous migration—that is, the target database is an Oracle database as well. A heterogeneous migration involves moving to an AWS Cloud-native database, such Amazon Aurora, Amazon DynamoDB, or Amazon RedShift, or an open-source database engine, like MySQL, PostgreSQL, or MariaDB.
Depending on your migration timetable and the amount of downtime you can tolerate, you have two options for moving an Oracle database from an on-premises system to the AWS Cloud: online migration or offline migration.
Offline Migration : When your application can afford a scheduled outage, you should use the offline migration approach. The source database is unavailable throughout the offline migration process. The data is transferred from the offline source database to the AWS target database. Validation and verification procedures are carried out following the migration to guarantee data consistency with the source database. You execute a cutover to AWS by connecting your application to the target database on AWS once the database has passed all validation tests.
Online migration: Use this technique if your application needs very little to no downtime. The source database is moved to AWS in stages when migrating online. While the source database is still operating, the first steps involve copying the data from the source database to the target database. All changes made in the source database are transferred to the target database in the following steps. The source and target databases are prepared for cutover when they are in sync. The program disconnects all connections to the source database during the cutover and redirects them to the target database on AWS. To synchronize the source and target databases, you can utilize Quest SharePlex, Oracle GoldenGate, AWS Database Migration Service (AWS DMS), or solutions from the AWS Marketplace (like Attunity).