The Evolution and Benefits of Oracle Change Data Capture

The Evolution and Benefits of Oracle Change Data Capture

What is Oracle Change Data Capture (CDC) and what are the benefits that it brings to the table? This post will answer all these questions and more, starting from the evolution of the Oracle CDC, the present form, the advantages that it offers, and the different types of Oracle Change Data Capture. 

One of the main reasons why Oracle CDC is a much-used feature in database management systems the world over is because it reduces database operating costs while boosting performance. 

So, let us dive into the various intricacies of Change Data Capture in general and Oracle CDC in particular. 

Before going into the features of Oracle CDC, let us first understand how Change Data Capture works, regardless of the database it is used in.

Change Data Capture is a software pattern optimized to track changes made in a source database. These changes are then monitored and action is taken based on the records of these changes. CDC also helps to integrate data by identifying, capturing, and delivering changes made to a source business database.  

The Evolution Of Oracle CDC

The Oracle Database Management System (DMS) is one of the oldest database systems in the world and is widely used by organizations around the globe. The CDC feature was launched by Oracle with its 9i version and came out of the box. 

Its primary purpose was to track and record changes made to databases in user tables that were then stored in change tables. By using the Extract, Transfer, and Load (ETL) application, these changes were then processed and moved to databases and data warehouses.

The downside of this pioneering feature was that triggers had to be placed in databases if the CDC had to work optimally. However, this type of technology slowed down the performance of databases and was not received well by DBAs. Based on this feedback, this Oracle CDC was modified and a new version of CDC named Oracle Streams was introduced with the 10g version.  

This feature met with great success as it used the redo logs of the source database along with the replication tool of Oracle, also a built-in feature. This form of Oracle CDC could track changes made at the source database and transfer them to the target database without lowering the source system speed or performance.  

Surprisingly, even though Oracle Streams was very well received by users, it was discontinued by Oracle from its 12c version. If users wanted the Oracle CDC feature they could get it through GoldenGate by paying for it.  

The Functioning of Oracle Change Data Capture   

The main work of the Oracle CDC feature is to enable real-time integration of data throughout an organization, simultaneously increasing the performance, speed, and access to databases. Further, this CDC automatically transfers incremental data, that is data generated after the last migration, from the source to a target database or data warehouse. 

When the most optimized tools are used for Oracle CDC, it can carry out several replication activities at a time without adversely affecting database performance. These activities include migrating databases to the cloud and filtering queries from databases in production to data warehouses. 

What makes this form of Oracle CDC technology outstanding is that all transfers from the source database are possible without shutting down systems. This aspect is very crucial for large data-driven organizations as downtime can upset their operating routines very badly.    

Oracle CDC is typically present in a data warehouse environment or a data repository platform since its main function is to capture and preserve the state of the data. The feature can be easily set up by users through physical storage, application logic, or a combination of the two.  

The Latest Version of Oracle CDC

There have not been any major changes in the basic concept of Oracle CDC from its 10g version to the modern era. Today too, it tracks and monitors changes made to the source database for taking action based on them at a later stage. The source and the target databases are not required to be different for Oracle CDC to function optimally, it works equally well when both are the same. 

The driving force behind the Oracle CDC is the Oracle Integrator. All changes made in the source database that will be used in other applications are identified by it. The Oracle Integrator supports two journalizing modes. 

The first is the Simple Journalizing Mode where all changes made to data in a system are monitored by Oracle CDC. 

The second is the Consistent Set Journalizing Mode where the referential integrity of the data between data stores is checked by Oracle CDC first before tracking any changes made to data.  

Both modes can be seamlessly set up on an Oracle Data Integrator. 

Benefits of the Oracle Change Data Capture

Here are some key benefits of Oracle CDC

# All changes such as Insert, Delete, and Update are captured by Oracle CDC along with their values both before and after the changes. 

# CDC packages publish and subscribe interfaces such as DBMS_CDC_PUBLISH and DBMS_CDC_SUBSCRIBE

# Oracle CDC greatly reduces the cost of database maintenance since data extraction from an Oracle database can be seamlessly carried out.  

Types of Oracle Change Data Capture

Oracle CDC comes in two types.  

# Synchronous CDC where triggers placed on records in a changed table are activated whenever a change occurs. The downside is that database speed and performance are often affected.

# Asynchronous CDC where redo files receive data and data changes are captured only when a SQL statement performs a DML activity. Forms of Asynchronous CDC are HotLog, Distributed HotLog, and AutoLog.

Over the years organizations have seamlessly carried out migration and replication actions with the very effective Oracle CDC.  

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