DMS - Database Migration Service

• Allows us to quickly and securely migrate databases to AWS
• It is resilient and self healing
• The source database remains available during migration
• Supports:
  • Homogeneous migrations: example Oracle to Oracle
  • Heterogeneous migrations: example Microsoft SQL Server to Aurora
• Supports Continuous Data Replication using CDC
• To use DMS we must create an EC2 instance to perform the replication tasks

DMS Sources and Targets

• Sources:
  • On-premises and EC2 instance database: Oracle, MS SQL Server, MySQL, MariaDB, PostgreSQL, MongoDB, SAP, DB2
  • Azure: Azure SQL Database
  • Amazon RDS: all including Aurora
  • Amazon S3
  • DocumentDB
• Targets:
  • On-premises or databases running on EC2 instance: Oracle, MS SQL Server, MySQL, MariaDB, PostgreSQL, SAP
  • Any DB in Amazon RDS
  • Redshift, DynamoDB, S3
  • OpenSearch Service
  • Kinesis Data Streams
  • Apache Kafka
  • DocumentDB and Amazon Neptune
  • Redis and Babelfish

AWS Schema Conversion Tool (SCT)

• Used to convert database schemas from one engine to another
• Example:
  • OLTP: SQL Server or Oracle to MySQL, Postgres, Aurora
  • OLAP: Teradata or Oracle to Redshift
• SCT is not required to be used in case we are migrating to the same DB engine

Mutli-AZ Deployments with DMS

• In case Multi-AZ is enabled, DMS provisions and maintains a synchronous standby replica in a different AZ
• Advantages:
  • Provides data redundancy
  • Eliminates I/O freezes
  • Minimizes latency spikes

Replication Task Monitoring

• Task Status:
  • Indicates the condition of the task (Created, Running, Stopped)
  • Task Status Bar: gives an estimation of the Task’s progress
• Table State:
  • Includes the current states of the tables
  • We get information about number of inserts, deletions and updates for each table

CloudWatch Metrics from DMS

• Host Metrics:
  • Performance and utilization statistics for the replication host
  • Example: CPUUtilization, FreeableMemory, FreeStorageSpace, WriteIOPS
• Replication Task Metrics:
  • Statistics for Replication Task including incoming and committed changes, latency between the replication host and both source and target databases
  • Example: FullLoadThroughputBandwidthTarget, FullLoadThroughputRowsTarget, CDCIncomingChanges, CDCLatencySource, CDCLatencyTarget, CDCChangesMemorySource, CDCChangesMemoryTarget
• Table Metrics:
  • Statistics for tables that are in the process of being migrated