Migrating Databases Using AWS DMS

Overview

Database migration is one of the most important tasks during cloud adoption and modernization projects. Organizations often need to move databases from on-premises environments to AWS or between different database platforms with minimal downtime.

Traditionally, database migration was a complex, time-consuming process that required manual effort, long maintenance windows, and extensive infrastructure management. AWS offers AWS Database Migration Service (AWS DMS), a fully managed service that helps businesses safely and effectively migrate databases, making the process easier.
AWS DMS supports homogeneous migrations (same database type) and heterogeneous migrations (different database types). It also supports continuous replication using Change Data Capture (CDC), making it suitable for production workloads with minimal downtime requirements.

This blog explains AWS DMS in simple language, including its architecture, workflow, migration types, benefits, security considerations, and cost overview.

Introduction

AWS Database Migration Service is a fully managed AWS service that securely migrates databases from one environment to another with minimal downtime.

AWS DMS helps organizations migrate:

• On-premises databases to AWS
• AWS databases to AWS
• Cloud databases to AWS
• Different database engines on another platform

Some commonly supported databases include:

• MySQL
• PostgreSQL
• Oracle
• SQL Server
• MongoDB
• Amazon RDS
• Amazon Aurora

AWS DMS reduces operational complexity because AWS manages the migration infrastructure automatically

AWS DMS

AWS DMS is a replication service that copies data from a source database to a target database.

It supports:

• One-time migration
• Ongoing replication
• Continuous synchronization

AWS DMS can migrate databases with very little downtime by continuously replicating changes from the source database to the target database.

Why Organizations Use AWS DMS?

Organizations use AWS DMS because it provides:

• Minimal downtime migration
• Automated database replication
• Secure data transfer
• Scalable migration infrastructure
• Support for multiple database engines
• Easy cloud adoption

It is commonly used during:

• Cloud migration projects
• Data center modernization
• Database upgrades
• Disaster recovery setups
• Analytics integration

AWS DMS Architecture Components

1. Source Database

The source database is the existing database from which data is copied.

Examples:

• On-premises MySQL
• MongoDB Atlas
• Oracle database
• SQL Server

2. Target Database

The target database is the destination for the data migration.

Examples:

• Amazon RDS
• Amazon Aurora
• Amazon S3
• PostgreSQL
• Amazon Redshift

3. Replication Instance

The replication instance is the core compute resource used by AWS DMS.

It performs:

• Data reading
• Data replication
• Migration processing
• Monitoring

AWS automatically manages the infrastructure.

4. Endpoints

Endpoints define the source and target database connection details.

They include:

• Hostname
• Port
• Username
• Password
• Database name

5. Migration Task

The migration task defines:

• What data to migrate
• Migration type
• Table selection
• Replication settings

Types of Migration in AWS DMS

1. Full Load Migration

In Full Load migration:

• Existing data is copied once
• No continuous replication occurs

Best for:

• Small migrations
• One-time data movement

2. Change Data Capture (CDC)

CDC continuously captures database changes, such as:

• Inserts
• Updates
• Deletes

These changes are replicated to the target database in near real-time.

Best for:

• Production migrations
• Minimal downtime requirements

3. Full Load + CDC

This is the most commonly used migration type.

Process:

1. Existing data is copied
2. Ongoing changes continue syncing

This ensures:

• Minimal downtime
• Continuous synchronization

Step-by-Step AWS DMS Workflow

Step 1: Create Replication Instance

• Create the DMS replication instance inside a VPC.

Step 2: Configure Source Endpoint

Add:

• Source database hostname
• Port
• Credentials

Step 3: Configure Target Endpoint

Add target database details.
Step 4: Test Endpoint Connectivity

AWS DMS validates database connectivity.
Step 5: Create Migration Task

Choose:

• Full load
• CDC
• Full load + CDC

Select the required tables.

Step 6: Start Migration

AWS DMS begins copying data from the source to the target.
Step 7: Monitor Migration

Use Amazon CloudWatch and the AWS DMS console for monitoring:

• Replication lag
• Errors
• Task health

Benefits of AWS DMS

This architecture provides secure connectivity by allowing AWS Glue to remain inside a private subnet while securely accessing MongoDB Atlas through a NAT Gateway. Using an Elastic IP ensures a fixed public IP address, enabling predictable, reliable IP whitelisting on MongoDB Atlas. The solution is highly scalable because AWS Glue automatically scales based on workload requirements without manual intervention. Additionally, it reduces operational overhead by eliminating the need to manage EC2-based ETL servers and infrastructure manually. The overall setup also follows AWS networking and security best practices, making it a production-ready solution for secure and scalable data integration workloads.

Conclusion

AWS Database Migration Service (AWS DMS) is a powerful, beginner-friendly service for securely migrating databases with minimal downtime. It supports multiple database engines, continuous replication, and scalable migration workflows, without requiring organizations to manage complex infrastructure manually.

For beginners starting their cloud migration journey, AWS DMS is an excellent service to learn from because it combines networking, security, database management, and cloud automation into a single practical solution.

Drop a query if you have any questions regarding AWS DMS, and we will get back to you quickly.