AWS Database Migration Service FAQs


Q: What is AWS Database Migration Service?

AWS Database Migration Service (AWS DMS) is a managed migration and replication service that helps you move your databases and analytics workloads to AWS quickly and securely. The source database remains fully operational during the migration, minimizing downtime to applications that rely on the database.

The AWS Database Migration Service can assess, convert, and migrate your data to and from the most widely used commercial and open-source databases. AWS Database Migration Service supports homogeneous migrations such as Oracle to Oracle, as well as heterogeneous migrations between different databases, such as Oracle or Microsoft SQL Server to Amazon Aurora.

With AWS Database Migration Service, you can also continuously replicate data with low latency from a supported source to a supported target. For example, you can replicate from multiple sources to Amazon Simple Storage Service (Amazon S3) to build a highly available and scalable data lake solution.

You can also consolidate databases into a petabyte-scale data warehouse by streaming data to Amazon Redshift. Learn more about the supported source and target databases.

Q: How do I get started with AWS Database Migration Service?

Getting started with AWS Database Migration Service is quick and simple. Most data replication tasks can be set up in less than 10 minutes.

Visit the AWS Database Migration Service section of the AWS Management Console and enter the Start Migration wizard. Specify your source and target endpoints, select an existing replication instance or create a new one, and accept the default schema mapping rules or define your own transformations. Data replication will start immediately after you complete the wizard.

Q: How much does AWS DMS cost?

AWS DMS is an affordable, low-cost option to migrate your databases and analytics workloads. You pay only for the replication instances and any additional log storage. Data transfer is free. You can find full pricing details on the DMS pricing page.

Q: How much does AWS DMS Schema Conversion cost?

AWS DMS Schema Conversion is free to use as a part of DMS. Pay only for the storage used.

Q. What are the database migration steps when using AWS Database Migration Service?

During a typical simple database migration, you will create a target database, migrate the database schema, set up the data replication process, initiate the full load and a subsequent change data capture and apply, and conclude with a switchover of your production environment to the new database once the target database is caught up with the source database.

Q. Is the database migration process using AWS DMS different for continuous data replication?

The only difference is in the last step (the production environment switchover), which is absent for continuous data replication. Your data replication task will run until you change or terminate it.

Q: Can I monitor the progress of a database migration task?

Yes. AWS Database Migration Service has a variety of metrics displayed in the AWS Management Console. It provides an end-to-end view of the data replication process, including diagnostic and performance data for each point in the replication pipeline.

AWS Database Migration Service also integrates with other AWS services such as CloudTrail and CloudWatch Logs. You can also leverage the AWS Database Migration Service API and AWS Command Line Interface (AWS CLI) to integrate with your existing tools or build custom monitoring tools to suit your specific needs.

Q: How do I integrate AWS Database Migration Service with other applications?

AWS Database Migration Service provides a provisioning API that allows creating a replication task directly from your development environment, or scripting their creation at scheduled times during the day.

The service API and CLI allows developers and database administrators to automate the creation, restart, management and termination of replication tasks.

Supported sources and target engines

Q: What source databases and target databases does AWS Database Migration Service support?

AWS Database Migration Service (DMS) supports a range of homogeneous and heterogeneous data replications.

Either the source or the target database (or both) need to reside in RDS or on EC2. Replication between on-premises to on-premises databases is not supported.

Q: What sources and targets does AWS DMS Schema Conversion support?

AWS DMS Schema Conversion supports a range of popular databases, which are listed here.

Q: What sources and targets does AWS Schema Conversion Tool support?

AWS Schema Conversion Tool (SCT) supports a range of database and data warehouse conversions, which are listed here.

Schema conversion

Q. Will AWS Database Migration Service help me convert my Oracle PL/SQL and SQL Server T-SQL code to Amazon RDS or MySQL and PostgreSQL stored procedures?

Yes, part of the AWS Database Migration Service is AWS DMS Schema Conversion (DMS SC) which automates the conversion of Oracle PL/SQL and SQL Server T-SQL code to equivalent code in the Amazon RDS / MySQL dialect of SQL or the equivalent PL/pgSQL code in PostgreSQL.

When a code fragment cannot be automatically converted to the target language, DMS SC will clearly document the locations that require manual input from the application developer. A downloadable version, called AWS Schema Conversion Tool (SCT), is also available.

Q: Does AWS Database Migration Service migrate the database schema for me?

When you need to use a more customizable schema migration process (for example, when you are migrating your production database and need to move your stored procedures and secondary database objects), you can use the built-in Schema Conversion feature of AWS DMS for heterogeneous migrations. Alternative options include downloading AWS Schema Conversion Tool or using the schema export tools native to the source engine, if you are doing homogeneous migrations such as:

  1. SQL Server Management Studio's Import and Export Wizard.
  2. Oracle's SQL Developer Database Export tool or script the export using the dbms_metadata package.
  3. MySQL's Workbench Migration Wizard.

Q. How are AWS Database Migration Service (DMS) and AWS Schema Conversion Tool (SCT) related?

When choosing to use SCT versus the built-in DMS Schema Conversion feature, DMS and SCT work in conjunction to both migrate databases and support ongoing replication for a variety of uses such as populating data lakes and warehouses, synchronizing systems, and so on. SCT can copy database schemas for homogeneous migrations and convert them for heterogeneous migrations. The schemas can be between databases (for example, Oracle to PostgreSQL), or between data warehouses (for example, Netezza to Amazon Redshift).

Once a schema has been created on an empty target, depending on the volume of data and/or supported engines, either DMS or SCT are then used to move the data. DMS traditionally moves smaller relational workloads (<10 TB) and MongoDB, whereas SCT is primarily used to migrate large data warehouse workloads. DMS supports ongoing replication to keep the target in sync with the source; SCT does not.

Data replication

Q: In addition to one-time data migration, can I use AWS Database Migration Service for continuous data replication?

Yes, you can use AWS Database Migration Service for one-time data migration into RDS and EC2-based databases as well as for continuous data replication. AWS Database Migration Service will capture changes on the source database and apply them in a transactionally consistent way to the target.

Continuous replication can be done from your data center to the databases in AWS or in the reverse, replicating to a database in your data center from a database in AWS. Ongoing continuous replication can also be done between homogeneous or heterogeneous databases. For ongoing replication, it would be preferable to use Multi-AZ for high availability.

Q. Why should I use AWS Database Migration Service instead of my own self-managed replication solution?

AWS Database Migration Service is very simple to use. Replication tasks can be set up in minutes instead of hours or days, compared to the self-managed replication solutions that have to be installed and configured. AWS Database Migration Service monitors for replication tasks, network or host failures, and automatically provisions a host replacement in case of failures that can’t be repaired. Users of AWS Database Migration Service don’t have to overprovision capacity and invest in expensive hardware and replication software, as they typically have to do with self-managed solutions.

With AWS Database Migration Service users can take advantage of on-demand pricing and scale their replication infrastructure up or down, depending on the load. AWS Database Migration Service data replication integrates tightly with the AWS Schema Conversion Tool, simplifying heterogeneous database migration projects.

Q: Can I replicate data from encrypted data sources?

Yes, AWS Database Migration Service can read and write from and to encrypted databases. AWS Database Migration Service connects to your database endpoints on the SQL interface layer. If you use the Transparent Data Encryption features of Oracle or SQL Server, AWS Database Migration Service will be able to extract decrypted data from such sources and replicate it to the target.

The same applies to storage-level encryption. As long as AWS Database Migration Service has the correct credentials to the database source, it will be able to connect to the source and propagate data (in decrypted form) to the target.

We recommend using encryption-at-rest on the target to maintain the confidentiality of your information. If you use application-level encryption, the data will be transmitted through AWS Database Migration Service as is, in encrypted format, and then inserted into the target database.

Migration planning

Q. What is AWS DMS Fleet Advisor?

AWS DMS Fleet Advisor is a free, fully managed capability of AWS Database Migration Service (AWS DMS). It automates migration planning and helps you migrate database and analytics fleets to the cloud at scale with minimal effort.

Q. When should I use AWS DMS Fleet Advisor versus AWS Application Discovery Service and Migration Evaluator?

AWS DMS Fleet Advisor is intended for users looking to migrate a large number of database and analytics servers to AWS. When you are ready to migrate your database and analytics workloads to target services in AWS, you should use AWS DMS Fleet Advisor to discover and analyze your Online Transaction Processing (OLTP) and Online Analytical Processing (OLAP) database workloads. Fleet Advisor allows you to build a customized migration plan by determining the complexity of migrating your source databases to target services in AWS.

The AWS Application Discovery Service (ADS) and Migration Evaluator are targeted for broad-based compute and attached block storage discovery. The Migration Evaluator is used by customers starting their migration journey who are looking for a data-driven business case for AWS. ADS is used to feed the AWS Migration Hub to visualize server to server dependencies, create application groups, and track migration progress.

Q. When should I use AWS DMS Fleet Advisor in conjunction with AWS Application Discovery Service and Migration Evaluator?

Migration Evaluator and AWS Application Discovery Service help you gain early insights into the inventory portfolio of your entire on-premises data center. When you are ready to perform a deeper analysis of your database and analytics workloads to determine the migration paths in AWS, you should use AWS DMS Fleet Advisor to create a database migration plan to AWS.

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