AWS Database Migration Service

Overview

• Online database migration
• Creates tables, loads data, keeps it sync
• Agentless (uses Replication Instance)

Engines

• Supports
  • MySQL
  • MariaDB
  • PostgreSQL
  • Oracle
  • SQL Server
  • Aurora
  • Redshift

Model

• Environments
  • on-premise
  • AWS (EC2, RDS)
• Heterogenous migration possible (e.g. Oracle -> MySQL)
• Does not propagate most of DDL (indexes, sprocs, etc.)
  • Must be replicated manually
• To obtain changes it calls database's change capture API
  • Oracle: log miner
  • MySQL:  binlog API
  • PostgreSQL: replication slots

Endpoint

• "Conection String" to the database
• required for source/target

Replication Instance

• EC2 instance
• Performs actual work
• Similar to data pipeline
• Instance Types
  • C4 (e.g. dms.c4.large), 100GB gp2
  • T2 (e.g. dms.t2.micro), 50GB gp2
• Public IP - needed only when source/target accessible over Internet

Migration Task

• Which schema/tables to migrate
• Migration Type
  • Full Load, Ongoing Replication
  • Ongoing Replication
  • Full Load
• Endpoints (source/target)

Encryption

• Encrypts storage used by replication instance and endpoint connection
• Uses KMS (aws/dms) 

Use Cases

• One time migration
• Continous replication (e.g. prod->test)
• Move shards between servers
• Moving off commercial database
• Hybrid deployments
• Integrate tables from 3rd party tools (e.g. PeopleSoft)

References

• https://www.youtube.com/watch?v=nMTtQOtgp9g&t=2551s