Oracle Change Data Capture – Development and Benefits

1. Oracle Change Data Capture – Development and Benefits

2. Oracle Change Data Capture (CDC) is a technology that is widely used today for multiple activities that are critical in today’s organizations. CDC is optimized for detecting and capturing insertions, updates, and deletions that are applied to tables in an Oracle database. The technology is also an essential feature of any Oracle replication solution as CDC classifies and records changed data in a relational format that is suitable for use in EAI, ETL, and other applications.

3. Businesses using Oracle databases from Oracle CDChave several advantages. Data warehousing costs are lower and real-time data integration done by extracting and loading data into data warehouses and other data repositories incrementally and in real-time are allowed. When only the data that has changed after the last extraction is transferred, Oracle CDC does away with the need for bulk data updating, batch windows, and complete data refreshes that can disrupt users and businesses.

5. Development of Log-Based Oracle CDC • The Oracle 9i version of Oracle was released in 2001 with a new feature. Users of the database had access to a built-in mechanism for tracking and storing changes in real-time as they happened – a native Oracle CDCfeature. However, database administrators faced a major disadvantage as it depended on placing triggers on tables in the source database, thereby increasing processing overheads. • This feature was fine-tuned in the Oracle 10g model. A new Oracle CDC technology was introduced that used the redo logs of a database to capture and transmit data without using the previous invasive database triggers. An Oracle replication tool called Oracle Streams was used for this activity. • This new version of Oracle CDC was primarily log-based form of change data capture that was lightweight and did not need the structure of the source table to be changed. Even though this latest model of CDC became quite popular, Oracle decided to withdraw support to Oracle CDC with the release of Oracle 12c. Users were encouraged to switch to the higher-priced Oracle Golden Gate, an Oracle replication software solution.   • Oracle CDC Modes • The Oracle Data Integrator supports two journalizing modes. • The first is the Synchronous Mode. Here triggers are placed in tables in the source database and all changed data at source is immediately captured. Each SQL statement in the table completes a Data Manipulation Language (DML) activity which is insert, update, or delete. The changed data is captured as an integral component of the transaction which changed the data at the source. This mode of Oracle CDCis available in the Oracle Standard and the Oracle Enterprise Editions.

6. The next is the Asynchronous Mode. Here, data is sent to redo log files where the changed data is captured after a SQL statement goes through a DML activity. Since the modified data is not captured as a part of the transactions that made changes to the source table, this mode does not have any impact on the transaction