Announcing Public Preview Availability of Azure SQL Database Online Migration in Azure Database Migration Service


In an era of exploding data volumes and ever-changing business requirements, we understand that a streamlined and robust migration service is key to accelerating customers’ transition to the cloud.  Since database migrations can lead to significant downtimes, how can customers deal with database migrations when they need to minimize end-user downtime but also want to ensure that the data remains up-to-date with the source database?

Today, we are very excited to announce public availability of online migration in Azure Database Migration Service (DMS). DMS is a one-stop shop for migrating data from different database engines to Azure with built-in resiliency and robustness. With online migration, businesses can migrate their databases to Azure while the databases continue to be operational. In other words, migrations can be completed with minimum downtime for critical applications, limiting the impact to service level availability and inconvenience their end customers.

DMS also introduces the Business Critical pricing tier supports offline and online migrations for business critical workloads that require minimal downtime. The Business Critical pricing tier is currently available free in public preview.

Online migration is available for customers to migrate on-premises/SQL Server on IaaS workloads to Azure SQL Database in the following regions:

  • West Europe
  • East US2
  • Central US

We will be extending online migration to other regions in a staged approach, and in addition, migrating from on-premises SQL Server/RDS workloads to Azure SQL Database Managed Instance will be available in the near future.

Setting up an online migration in DMS is very simple. DMS first performs the full data load and establishes a continuous sync with the target databases until the customer initiates the cutover migration at a convenient time. A short video describing this process and providing a demonstration follows.

Note: You can also access this video directly here: Online migrations using Azure Database Migration Service.

Limitations and Known issues:

Known issues and limitations associated with online migrations are below.

Online migrations are not supported for temporal tables.
Tables with hierarchyid data types are not supported.
LOB Data types: If the length of Large Object (LOB) column is bigger than 32 KB, data might gets truncated at the target.

To get the complete list of limitations and known issues, please visit our known issues page.

Please refer to the resources below for online migration. If you have any questions, please email the DMS Feedback alias at dmsfeedback@microsoft.com.

Thank you.

Raj Pochiraju
Principal Program Manager
Azure Data Engineering

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