90. AWS Database Migration Service

琴光亮

2023-12-01

Overview

AWS Database Migration Service (AWS DMS) is a web service that you can use to migrate data from a source data store to a target data store.
AWS Database Migration Service (AWS DMS) is a cloud service that makes it easy to migrate relational databases, data warehouses, NoSQL databases, and other types of data stores.
With AWS DMS, you can perform one-time migrations, and you can replicate ongoing changes to keep sources and targets in sync
If you want to migrate to a different database engine, you can use the AWS Schema Conversion Tool (AWS SCT) to translate your database schema to the new platform.
At a basic level, AWS DMS is a server in the AWS Cloud that runs replication software.
- You create a source and target connection to tell AWS DMS where to extract from and load to.
- Then you schedule a task that runs on this server to move your data.
The only requirement to use AWS DMS is that one of your endpoints must be on an AWS service. You can't use AWS DMS to migrate from an on-premises database to another on-premises database.

At a high level, when using AWS DMS you do the following:
- Create a replication server.
- Create source and target endpoints that have connection information about your data stores.
- Create one or more migration tasks to migrate data between the source and target data stores.
A task can consist of three major phases:
- The full load of existing data
  - During a full load migration, where existing data from the source is moved to the target, AWS DMS loads data from tables on the source data store to tables on the target data store.
  - While the full load is in progress, any changes made to the tables being loaded are cached on the replication server; these are the cached changes.
- The application of cached changes
  - When the full load for a given table is complete, AWS DMS immediately begins to apply the cached changes for that table.
- Ongoing replication
  - Once the table is loaded and the cached changes applied, AWS DMS begins to collect changes as transactions for the ongoing replication phase.
  - If a transaction has tables not yet fully loaded, the changes are stored locally on the replication instance.
  - After AWS DMS applies all cached changes, tables are transactionally consistent.
  - At this point, AWS DMS moves to the ongoing replication phase, applying changes as transactions.

AWS DMS provides support for data validation to ensure that your data was migrated accurately from the source to the target. If enabled, validation begins immediately after a full load is performed for a table.