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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