AWS Database Migration Service & Application Migration
7 questions found
What is AWS Database Migration Service and what problem does it solve?
Beginner
AWS Database Migration Service, or DMS, is a fully managed service that helps you migrate databases into AWS quickly and securely, supporting both homogeneous migrations between the same database engine and heterogeneous migrations between different database engines, such as moving from Oracle to PostgreSQL, while keeping the source database fully operational and minimizing downtime during the actual cutover.
aws dms create-replication-task --replication-task-identifier my-migration-task --source-endpoint-arn arn:aws:dms:us-east-1:123456789012:endpoint:source --target-endpoint-arn arn:aws:dms:us-east-1:123456789012:endpoint:target --migration-type full-load-and-cdc
Real-world example
A retail company migrates its on premises Oracle database to Amazon RDS for PostgreSQL using DMS, which handles both the initial bulk data transfer and the ongoing replication of new changes, allowing the production system to keep running throughout the migration.
Common follow-ups: What is the difference between homogeneous and heterogeneous migrations?;How does DMS handle schema differences between different database engines?
RDS & Databases;AWS Direct Connect & Hybrid Connectivity
What is the AWS Schema Conversion Tool, and how does it work alongside DMS for heterogeneous migrations?
Beginner
The AWS Schema Conversion Tool, or SCT, analyzes your source database schema and automatically converts it into an equivalent schema compatible with your target database engine, handling differences in data types, stored procedures, and functions between different database systems, and it is typically used before running DMS, which then handles the actual movement of the data itself once the schema has been properly converted on the target side.
// SCT converts Oracle PL/SQL stored procedures
// into equivalent PostgreSQL PL/pgSQL functions automatically
Real-world example
A company migrating from Microsoft SQL Server to Amazon Aurora PostgreSQL uses the Schema Conversion Tool to automatically translate the majority of its stored procedures into PostgreSQL compatible syntax, significantly reducing the amount of manual rewriting needed.
Common follow-ups: What percentage of a typical schema can SCT convert automatically without manual intervention?;What happens to database objects that SCT cannot automatically convert?
RDS & Databases;Amazon Redshift & Data Warehousing
How does DMS support continuous data replication using change data capture to minimize downtime during a migration?
Intermediate
DMS change data capture, or CDC, continuously monitors the source database's transaction logs for new changes after the initial full data load has completed, applying those same changes to the target database in near real time, meaning the target database stays continuously synchronized with the source right up until the moment you are ready to perform a final cutover, dramatically reducing the actual downtime window compared to a traditional one time data dump migration approach.
aws dms modify-replication-task --replication-task-arn arn:aws:dms:us-east-1:123456789012:task:my-task --migration-type cdc
Real-world example
A company migrating a critical customer database keeps the target database continuously synchronized using DMS CDC for two weeks while thoroughly testing the new environment, then performs a final cutover during a brief maintenance window with only a few minutes of actual downtime.
Common follow-ups: How does DMS handle conflicts if data changes on both source and target simultaneously?;What happens if CDC replication falls behind the source database's rate of change?
RDS & Databases;AWS Backup & Disaster Recovery
What is AWS Application Migration Service, and how does it support migrating entire servers, not just databases, into AWS?
Intermediate
AWS Application Migration Service, often called MGN, uses continuous block level replication to copy entire on premises or other cloud servers into AWS, including the full operating system, applications, and data, allowing you to launch fully functioning EC2 instances that are exact replicas of your original servers with minimal manual reconfiguration, which is significantly less effort than manually rebuilding an application from scratch in the cloud.
aws mgn start-replication --source-server-id s-1234567890abcdef0
Real-world example
An enterprise migrating dozens of legacy application servers from an on premises data center uses Application Migration Service to continuously replicate each server into AWS, then performs a test launch to validate everything works correctly before cutting over production traffic.
Common follow-ups: How does Application Migration Service differ from AWS Database Migration Service in terms of what they migrate?;What is involved in the cutover process once replication is complete?
EC2 & Compute;AWS Backup & Disaster Recovery
What migration strategies, commonly called the six Rs, are used when planning a large scale cloud migration?
Intermediate
The six common migration strategies include rehosting, which is a straightforward lift and shift of an application with minimal changes, replatforming, which makes small optimizations during the move, repurchasing, which replaces an existing application with a cloud based software as a service alternative, refactoring, which involves redesigning the application to be cloud native, retaining, which means keeping certain systems on premises for now, and retiring, which means decommissioning applications that are no longer needed at all.
// Example planning matrix
// Legacy CRM: repurchase with a SaaS alternative
// Custom internal app: rehost first, refactor later
Real-world example
A company migrating dozens of applications decides to simply rehost its stable but low priority internal tools using lift and shift, while committing to a full refactor for its core customer facing application to take advantage of cloud native scalability.
Common follow-ups: How do you decide which of the six Rs is appropriate for a specific application?;Which migration strategy typically delivers the fastest short term cost savings?
AWS Elastic Beanstalk;Well-Architected Framework
How can AWS Migration Hub provide centralized visibility and tracking across a large, multi application migration project?
Advanced
AWS Migration Hub provides a single location to track the progress of application migrations across multiple AWS migration tools, such as DMS and Application Migration Service, giving program managers and migration teams a consolidated view of which applications have been discovered, which are actively migrating, and which have completed, which is essential for coordinating a complex migration involving dozens or hundreds of individual servers and databases across many teams.
aws migrationhub create-progress-update-stream --progress-update-stream-name my-migration-project
Real-world example
A large enterprise migrating over two hundred servers and databases uses Migration Hub to give its migration program office a single dashboard showing the real time status of every application in the migration wave, rather than each team tracking progress in separate spreadsheets.
Common follow-ups: What discovery tools integrate with Migration Hub to assess an on premises environment before migration?;How does Migration Hub help identify dependencies between applications during planning?
AWS Application Migration Service;Well-Architected Framework
What are the key considerations for validating data integrity and application performance after completing a large scale database or application migration?
Advanced
Post migration validation typically involves running automated row count and checksum comparisons between the source and target databases to confirm data integrity, performing thorough functional and performance testing of the migrated application under realistic load, closely monitoring the new environment using CloudWatch for any unexpected errors or performance regressions, and maintaining the ability to roll back to the original environment for a defined period in case unexpected issues surface only after real production traffic begins flowing to the new environment.
aws dms describe-table-statistics --replication-task-arn arn:aws:dms:us-east-1:123456789012:task:my-task
Real-world example
A company completing a major database migration runs an automated row count and checksum validation script comparing the old and new databases before officially decommissioning the legacy system, catching a small data discrepancy that was then corrected before final cutover.
Common follow-ups: What tools are available to automate post migration data validation?;How long should an organization typically keep the old environment available as a rollback option?
Monitoring (CloudWatch);AWS Backup & Disaster Recovery