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Migrating SQL Databases from On-Premises to AWS

Migrating SQL databases from on-premises to the cloud has become increasingly common as businesses seek to leverage the scalability, flexibility, and cost-effectiveness of cloud platforms like Amazon Web Services (AWS). However, the process of migrating databases can be complex, with various options and considerations to take into account.

In this comprehensive guide, we will explore the different migration options available for SQL databases and focus specifically on migrating to Microsoft SQL Server on Amazon RDS within the AWS ecosystem. We will discuss the prerequisites, limitations, and architectural considerations for the migration process. Additionally, we will explore the tools and epics involved in successfully migrating SQL databases to AWS.

Understanding Migration Options

When it comes to migrating databases, there are three primary options to consider: rehost (IaaS), replatform (PaaS), and refactor (transform). Each option offers unique advantages and considerations, depending on factors such as migration timeline, costs, and desired outcomes.

Rehost (IaaS)

In the rehost option, the database is migrated as-is to the cloud. This means that a database running on a server is migrated to an Amazon EC2 instance.

Rehosting provides a straightforward migration process without the need for significant changes to the database structure or application code.

Replatform (PaaS)

With the replatform option, the database is migrated to a managed VM and database service, such as Amazon RDS.

Replatforming offers the benefits of managed services, including automatic backups, replication, and other administrative tasks handled by AWS.

Refactor (Transform)

Refactoring involves converting the database to a different software or technology, such as migrating from Microsoft SQL Server to an open-source database like MySQL or PostgreSQL.

Refactoring allows for the adoption of new technologies or platforms while requiring significant changes to the database schema and application code.

Migrating SQL Server Databases to AWS SQL (RDS)

In this guide, we will focus on migrating SQL Server databases to Amazon RDS, which is a managed SQL database service provided by AWS. This section will cover two primary methods: SQL Server backup and restore, and AWS Database Migration Service (DMS).

SQL Server Backup and Restore

Before initiating the backup and restore process, it is essential to ensure that the source database is disabled with write actions to prevent data inconsistencies during migration. Follow these steps for a successful backup and restore migration:

  • Perform a full backup/export of the SQL Server database on the source machine in the .bak format.
  • Copy the .bak file to an S3 bucket that is accessible by the role associated with Amazon RDS.
  • Execute the msdb.dbo.rds_restore_database stored procedure, providing the necessary parameters such as the database name, S3 ARN, recovery option, and optional parameters like the KMS master key ARN and the type of backup (differential or full).

Keep in mind that the backup and restore method is straightforward but may involve significant downtime, making it less suitable for highly available applications. Consider alternative approaches like the AWS Database Migration Service for minimizing downtime during application migrations.

AWS Database Migration Service (DMS)

AWS Database Migration Service (DMS) provides a robust solution for migrating databases to AWS. DMS allows for one-time migrations or continuous replication with ongoing changes. Follow these steps to perform a migration using DMS:

  • Create source and target endpoints, specifying the necessary credentials to access the databases.
  • Create a replication server with the desired size to facilitate the migration process.
  • Select the source and target endpoints for the migration.
  • Create a task and choose between a full load (one-time migration) or CDC (ongoing replication) based on your requirements. Run the task to initiate the migration process.

DMS offers a flexible and scalable solution for migrating SQL databases to AWS. It ensures minimal downtime and provides ongoing replication capabilities for seamless data synchronization.

Prerequisites and Limitations

Before initiating the migration process, certain prerequisites and limitations must be considered. These include:

  • An active AWS account: Ensure that you have an active AWS account to access the necessary services for the migration.
  • Microsoft SQL Server version: The migration options discussed in this guide support various versions of Microsoft SQL Server. Refer to the official AWS documentation for the latest information on supported versions.
  • Database size and network bandwidth: Consider the size of the database and available network bandwidth to estimate the migration duration and plan accordingly.

Ensure that you have met these prerequisites and understand the limitations before proceeding with the migration process.

Architecture Considerations

When migrating SQL databases to AWS, it is crucial to understand the source and target technology stacks and the overall target architecture. Let’s explore the architecture considerations for migrating SQL databases to Microsoft SQL Server on Amazon RDS:

Source Technology Stack

The source technology stack consists of the on-premises Microsoft SQL Server database that you intend to migrate. It includes the version of SQL Server and the supporting infrastructure.

Target Technology Stack

The target technology stack refers to Microsoft SQL Server on Amazon RDS. It involves provisioning an Amazon RDS instance and with connectivity to DMS replication instance/subnet.

Target Architecture

The target architecture for migrating SQL databases to AWS involves setting up the necessary infrastructure and configuring the components required for a successful migration. This includes creating an Amazon RDS instance and establishing connectivity between the source and target environments.

Tools for SQL Database Migration

To facilitate the migration process, several tools are available that can simplify and automate various tasks. These tools include:

  • AWS Data Migration Service (DMS): DMS is a fully managed service that streamlines database migration tasks, including schema conversion, data replication, and ongoing data synchronization.
  • Native Microsoft SQL Server tools: Microsoft provides several native tools for database migration, such as backup and restore, Copy Database Wizard, and copy and attach database. These tools can be used for on-premises to AWS migrations, depending on your requirements.
  • Third-party migration tools: Various third-party tools are available that offer advanced features for database migration. These tools often provide additional functionality and customization options.

Evaluate the available tools based on your specific requirements and choose the one that best suits your migration needs.

Best Practices for SQL Database Migration

To ensure a smooth and successful migration of SQL databases to AWS, it is essential to follow best practices. Here are some key considerations:

  1. Plan and test the migration: Develop a comprehensive migration plan and perform thorough testing to identify and address potential issues before the actual migration.
  2. Optimize the database: Prioritize database optimization to ensure efficient performance on the target environment. This may include index optimization, query tuning, and data compression.
  3. Secure the migrated database: Implement appropriate security measures, including encryption, access controls, and regular backups, to protect the migrated database from unauthorized access.
  4. Monitor and optimize costs: Regularly monitor and optimize costs associated with the migrated database by leveraging AWS cost management tools and adjusting resource allocations as needed.
  5. Establish a backup and recovery strategy: Implement a robust backup and recovery strategy to safeguard the migrated database against data loss or corruption. Consider utilizing AWS backup services or third-party solutions for enhanced data protection.

By adhering to these best practices, you can ensure a successful migration of your SQL databases to AWS.


Migrating SQL databases from on-premises to AWS offers numerous benefits, including scalability, flexibility, and cost-effectiveness. By understanding the available migration options, prerequisites, and limitations, and leveraging the appropriate tools and best practices, you can streamline the migration process and ensure a successful transition to the cloud.

Remember to thoroughly plan and test the migration, optimize the database for performance, secure the migrated database, monitor and optimize costs, and establish a robust backup and recovery strategy. With careful consideration and implementation, you can migrate your SQL databases to AWS and unlock the full potential of cloud computing.

For more information and detailed instructions on migrating SQL databases to AWS, refer to the official AWS documentation and additional resources provided below.

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