What is SQL Server Change Data Capture – Evolution and Function

 The goal of SQL Server CDC is to capture any changes made in a source database and present them to users in a simple relational format. Types of changes include insert, update, and delete to the database. All inputs required to capture these changes to the target, such as column information and metadata, are available for the modified and changed rows.

After the changes are made and noted in the tables at source, they are replicated in the column information of the target tables. As a matter of database safety and security, access to the changes is monitored closely.



Development of SQL Server CDC

It was in 2005 that Microsoft launched SQL Server CDC with “after update”, “after insert”, and “after delete” features. However, DBAs found its working quite complex. Based on this feedback, Microsoft introduced a revised version in 2008, which was very user-friendly, well-received, and is still in use today. In this version, database administrators can capture and store changes made to historical data directly without first carrying out some preparatory activities.  

The Working of SQL Server CDC

SQL Server CDC tracks and monitors all changes made to tables by users, which are then stored in relational tables that can be easily accessed and retrieved with T-SQL. Whenever the features and capabilities of the Change Data Capture technology are applied to a database table, a mirror image of the tracked table is created. It is possible to access the new audit tables after going through the SQL Server CDC activity for tracking the logged tables.

The source of all changes made to a database is reflected in the transaction log of SQL Server CDC. This log is now linked to the change table portion of the original table in the database.

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