DMS – Database Migration Services

DMS – Database Migration Services
-         https://docs.aws.amazon.com/dms/latest/userguide/Welcome.html
-         https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Introduction.html
-         A cloud service that makes it easy to migrate relational databases, data warehouses, NoSQL databases, and other types of data stores. You can use AWS DMS to migrate your data into the AWS Cloud, between on-premises instances (through an AWS Cloud setup), or between combinations of cloud and on-premises setups.
-         Can use DMS to migrate from one DB engine to another – either the source or the target needs to be on AWS. If need to migrate from on-premise to on-premise – AWS needs to be in the middle
-         Use the AWS Schema Conversion Tool (AWS SCT) to translate your database schema to the new platform – SCT creates tables, indexes, views on the Target database
-         Example: can facilitate migration from Azure onto AWS
-         Can do one-time migration OR on-going replication (primary / standby)
-         Resilient replication option (service failover is built in), fast, pay-as-you use – no upfront charges
-         Data encryption in-transit (SSL) and at-rest
-         Under the covers – AWS launches an EC2 instance, installs DMS software 
-         The launched instance can be large – 50-100GB – to accommodate for buffering in case reading from Source is faster that writing to Target
-         Homogenous vs heterogenous conversions: if migrating between databases of same type, the preferred approach is to use the native tools to migrate the schema; otherwise, if using different database products, use SCT to facilitate.
-         SCT workflow example; NoSQL migration to SQL database on AWS:
          §  Clone DC is used – not to disrupt the prod DB operations
          §  SCT extracts data from the clone and writes to S3
          §  Using DMS, SCT reads data form S3, creates DynamoDB tables, transforms data, writes into DynamoDB
-         Change data capture (CDC) might cause data to be written to disk, depending on how fast the target can write the changes
-         Optional - Multi-AZ set up can be used for resilience: a standby replication EC2 instance is created in an AZ away from the primary; primary is synchronously replicated to the standby replica. This is likely to consume more CPU as not only does the primary have to perform the data conversion from Source to Target, it also needs to keep the standby up to date. Need to select the EC2 type accordingly

-         The replication instance needs to be in VPC – with at least two subnets in a single AZ (multi-AZ – min 4 subnets total); need to set up set up security groups and NACLs.