Migrating your company’s databases to the cloud can feel like a monumental task. As you consider moving critical data securely, you’re likely asking how to migrate a database in AWS without disrupting your daily operations. The good news is that Amazon Web Services provides a powerful suite of tools designed to make this process smooth and manageable.

At Renova Cloud, we guide businesses through their cloud journey every day. A common project we handle is database migration. Let’s walk through how you can migrate a database in AWS, breaking down the strategies, tools, and steps you need to know for a successful transition.

What is AWS Database Migration Service?

The main tool for this job is the AWS Database Migration Service (AWS DMS). Think of it as a managed service that helps you move your databases to and from AWS with ease and security. One of its most significant advantages is that your original database can stay fully operational during the migration. This capability dramatically reduces downtime for the applications that depend on that database.

AWS DMS is incredibly flexible and supports two main types of migrations:

  • Homogeneous Migrations: This is when you move between the same database engines, like from an on-premises Oracle database to an Oracle database on AWS.
  • Heterogeneous Migrations: This is when you move between different database platforms, for example, from an Oracle database to Amazon Aurora MySQL.

For those more complex heterogeneous migrations, AWS DMS has a helpful partner called the AWS Schema Conversion Tool (AWS SCT). While DMS handles the job of moving the actual data, SCT takes care of converting your existing database schema. This includes objects like views, stored procedures, and triggers, translating them from the source engine’s format to one that’s compatible with your new target database.

What Migration Strategies Can You Use?

When you decide to migrate, you are not locked into a single method. Based on your database size, complexity, and downtime tolerance, you can choose from a few proven strategies. The provided AWS guide highlights three main approaches.

Native Database Tools

For smaller or simpler migrations, you can often use the native tools that come with your database engine. A great example is using mysqldump to perform a full data load for a MySQL database or pg_dump and pg_restore for PostgreSQL. Another is using Oracle Data Pump for an Oracle database. This method is often the simplest and most familiar to database administrators.

AWS DMS Only

You can also use AWS DMS to handle the entire process. This includes the initial full copy of your data, known as a full load, and the continuous capture of changes, called ongoing replication or Change Data Capture (CDC). Using DMS for everything gives you access to powerful built-in services like data validation, which are not available in most native tools.

The Hybrid Approach

A popular and highly effective strategy is the hybrid approach. This method combines the best of both worlds. You use a simple native tool for the initial full load of data. Then, you switch over to AWS DMS to handle the ongoing replication of any changes that happen after the initial copy is made.

This gives you the simplicity and speed of native tools for the heavy lifting upfront, plus the advanced features of AWS DMS for keeping your source and target databases perfectly synchronized with minimal downtime.

How Do You Plan a Full Load Migration?

The full load is the first major phase where you populate the target database with a copy of your source data. The tool you choose for this can have a big impact on the migration timeline, especially for large databases. A performance comparison in the AWS guide for a MySQL migration shows just how different these tools can be.

mysqldump

This native MySQL utility creates a logical backup of your database. It’s a good fit for smaller datasets, perhaps under 10 GB, where migration time isn’t a top concern. As the chart shows, it is the slowest of the three options tested.

mydumper and myloader

These are third-party utilities that improve uponmysqldump by performing multi-threaded backups. This parallel processing makes it much faster, especially for larger databases. If you cannot use Percona XtraBackup, mydumper is the next best option for performance.

Percona XtraBackup

For the best performance, especially on databases larger than 10 GB, Percona XtraBackup is the top choice. Unlike the other tools, it creates a physical backup of the database files instead of a logical one. 

This method is significantly faster. The AWS test showed it was four times faster than mysqldump and twice as fast as mydumper. If your situation allows for it, this tool is the best option for your full load.

The Main Steps of How to Migrate a Database in AWS

While every migration is unique, a typical project using AWS DMS follows a structured path. Let’s outline the fundamental steps you would take.

Phase 1: Assessment and Planning

Before you move a single byte of data, you need to understand what you are working with. The assessment phase is all about discovery. You need to take a complete inventory of your databases and the applications that depend on them. Identify the database engine, version, size, and performance characteristics.

During this phase, you will also define the goals of your migration. Are you looking to reduce costs, improve performance, or move away from a restrictive licensing agreement? Your goals will influence your choice of target database on AWS. For example, if you are migrating from Oracle, you might choose Amazon Aurora with PostgreSQL compatibility to escape expensive licensing fees.

This is also the time to use the AWS Schema Conversion Tool to create an assessment report. This report will give you a clear picture of the conversion complexity if you are planning a heterogeneous migration. Based on this information, you can create a detailed migration plan and timeline.

Phase 2: Schema and Code Conversion

Once you have a clear plan, the next step is to prepare the target environment. This involves setting up the necessary AWS infrastructure, including networking configurations and security groups. You will then create your target database instance, such as an Amazon RDS or Aurora cluster.

For heterogeneous migrations, this is where you will use AWS SCT to convert your source schema. You will connect SCT to both your source and target databases and let it perform the conversion. After the automated conversion is complete, your database administrators will need to review the results and manually address any items that SCT flagged. This might involve rewriting specific stored procedures or functions to be compatible with the new database engine. Once you are confident in the converted schema, you can apply it to your target database.

Phase 3: Data Replication and Migration

With the schema in place on your target database, it is time to move the data. This is where AWS Database Migration Service comes into play. You will configure a replication instance in AWS, which is a managed server that will perform the data migration tasks. Then, you will create source and target endpoints that tell DMS how to connect to your databases.

You will create a migration task in DMS to perform the actual data transfer. Typically, this starts with a full load, where DMS copies all the existing data from your source to your target. After the full load is complete, DMS can switch to Change Data Capture (CDC) mode. In this mode, it continuously replicates any new changes from the source to the target, keeping the two databases in sync. This ongoing replication is what makes a minimal-downtime migration possible.

Phase 4: Testing and Validation

You should never assume that a migration was successful without thorough testing. This phase is about validating that your data is accurate and your applications are working correctly with the new database.

First, perform data validation to ensure that the data in the target database is a perfect match for the data in the source. AWS DMS has built-in data validation capabilities that can compare the two and report any discrepancies.

Next, you need to conduct extensive application testing. Connect a non-production version of your application to the new database and run a full suite of tests. This should include performance testing, load testing, and functional testing to ensure that everything works as expected. It is better to discover any issues in a controlled testing environment rather than after you have gone live.

Phase 5: Cutover and Go Live

After all your testing is complete and you are confident that the new database is ready, it is time for the final cutover. The goal here is to switch your application from pointing to the old on-premises database to the new AWS database with as little disruption as possible.

Because you have been using CDC to keep the databases synchronized, the amount of downtime required for the cutover can be very short. The process typically involves these steps:

  1. Stop your application.
  2. Wait for the final few changes to replicate through DMS.
  3. Stop the DMS task.
  4. Point your application’s connection string to the new target database.
  5. Restart your application.

Once your application is running on the new database, perform a final round of health checks to confirm that everything is operating normally. You should keep your old database running for a short period as a fallback, but once you are fully confident in the new system, you can decommission your old on-premises infrastructure.

What About Complex Heterogeneous Migrations?

Migrating between different database engines, such as from Oracle to PostgreSQL, introduces another layer of complexity. Oracle’s PL/SQL procedural language is different from PostgreSQL’s PL/pgSQL, meaning your database code won’t work without changes.

This is where the AWS Schema Conversion Tool (SCT) becomes invaluable. SCT analyzes your source Oracle schema and automatically converts the majority of the database code, including stored procedures, functions, and triggers, into a format compatible with PostgreSQL. On average, SCT can successfully convert over 90% of the code, leaving only a small fraction for a database expert to handle manually.

A full Oracle to PostgreSQL migration is a comprehensive project. The AWS guide outlines a 12-step process that covers every phase, from initial design to post-production support. The effort is not just in moving data. As the breakdown shows, a large portion of the work is in application remediation and extensive testing.

The key steps in such a project include:

  • Future State Architecture Design
  • Database Schema Conversion (using SCT)
  • Application Conversion and Remediation
  • Script, ETL, and Report Conversion
  • Data Migration Mechanism (using DMS)
  • Testing and Bug Fixing
  • Performance Tuning
  • Post-Production Support

Start Your Migration with Confidence

Migrating a database to AWS is a strategic move that sets your business up for future growth and innovation. With powerful tools like AWS DMS and the Schema Conversion Tool, the question of how to migrate a database in AWS becomes more manageable and automated than ever before. Whether you’re performing a simple lift-and-shift or a complex heterogeneous migration, a clear strategy and the right tools make all the difference.

If you’re ready to take the next step but want an experienced partner to ensure a smooth transition, Renova Cloud is here to help. At Renova Cloud, a leading AWS Migration Competency Partner, we combine AWS-native tools with best-practice frameworks to ensure each migration is optimized for performance, security, and cost efficiency. We’ve helped financial and retail customers reduce migration downtime by 80% and cut legacy database licensing costs by up to 40%.

Why Work with an AWS Migration Competency Partner?

Partners like Renova Cloud are validated by AWS for technical proficiency and customer success in delivering secure, large-scale cloud migrations. This means our certified experts specialize in AWS database migrations and can help you plan, execute, and validate your project from start to finish.

Contact us today to learn how we can accelerate your journey to the cloud.