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Amazon Web Service Data Migration Service u2013 AWS DMS u2013 is a cloud-based service that ensures that migration is carried out seamlessly and effectively between relational databases, NoSQL databases, data warehouses, and more.
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Before starting on AWS Data Migration Service (DMS) and Change Data Capture, it is necessary to first understand the two concepts. Amazon Web Service Data Migration Service – AWS DMS – is a cloud-based service that ensures that migration is carried out seamlessly and effectively between relational databases, NoSQL databases, data warehouses, and more. It can also be used in AWS DMS CDCfor migrating data from on-premises database to the cloud, from one cloud-based database to another, and even in rare cases from a cloud database to an on-premises one. AWS DMS CDC can also be used to carry out a single migration or replicate changes in the database to ensure that both the source and the target database are always in sync. Being a part of AWS, all the advantages of a cloud-based service like security, cost efficiency, and flexibility are also available in AWS DMS.
Change Data Capture (CDC) identifies and captures changes and modifications that have been made to data or metadata after the last migration or replication. The changes are tracked in specific pre-set times which can be as close as minutes or seconds. The changes noticed are then copied into a different repository by the replication software of AWS DMS CDC. The CDC replication of batch load ensures that the target databases are always synchronized with the source database after each load is completed. As seen during the usual batch loads, CDC enables replication software while transferring one source to single or multiple targets.
AWS DMS CDCuses engine-centric API actions from the transaction logs of the source engine for identifying current changes from the source database. This is how it is done. · For Microsoft SQL Server, AWS DMS uses MS-Replication or MS-CDC to enter information to the SQL Server transaction log. · For Oracle, AWS DMS CDCuses either the Oracle LogMiner API or the binary reader API to track ongoing changes. AWS DMS reads ongoing changes from the online or archived redo logs based on the SCN (System Change Number). · For MySQL, AWS DMS reads changes from the row-based binary logs and loads them to the target. · For PostgreSQL, AWS DMS uses the test_decodingplugin and sets up logical replication slots to track changes from the source and migrate them to the target. · For Amazon RDS it is advisable to ensure AWS DMS CDCin backups. You can create an AWS DMS CDCtask while migrating data for capturing changes to the source database. This process is done once the full migration to a supported data store is completed. This is called ongoing replication and is undertaken when current changes from a source data store have to be replicated. It collects changes to the database logs by using the native API database engine. The utility of AWS DMS CDCis that source and target database retain data integrity and synchronizes even when changes take place.