{"id":410,"date":"2008-03-21T16:04:48","date_gmt":"2008-03-21T20:04:48","guid":{"rendered":"http:\/\/onlineappsdba.com\/index.php\/2008\/03\/21\/change-data-capture-oracle-cdc\/"},"modified":"2009-08-19T09:08:52","modified_gmt":"2009-08-19T13:08:52","slug":"change-data-capture-oracle-cdc","status":"publish","type":"post","link":"https:\/\/onlineappsdba.com\/index.php\/2008\/03\/21\/change-data-capture-oracle-cdc\/","title":{"rendered":"Change Data Capture – Oracle CDC"},"content":{"rendered":"

CDC<\/strong> : is database functionality that helps in capturing incremental changes to Oracle Database.<\/p>\n

Terminology in CDC
\n<\/u>Publisher<\/strong>: is database user that publishes captured changed data
\nSubscriber<\/strong>: is database user that consumes changed data
\nChange Tables<\/strong>: Changes in database are written to change tables
\nSubscriber Views<\/strong>: are database views against change tables for subscribers.<\/p>\n

Note* -> One publisher can support multiple subscribers<\/p>\n

CDC Implementation Methods
\n<\/u><\/strong>
\nA) Synchronous CDC<\/strong> – In this method changes are captured synchronously from source database into change tables. This method uses internal database triggers.<\/p>\n

B) Asynchronous Autolog CDC<\/strong>– This method requires staging database separate from source database. Redo logs are transferred from source database to staging database using redo transport service (You can also manually transfer redo and register them to staging database) and changes are captured at staging database. There are two modes available
\ni)<\/strong> Autolog online CDC\u00a0 ii)<\/strong> Autolog archived CDC<\/p>\n

– Source and Target database should be on same operating system and on same database version.
\n– SYS password on source and target database must be same.
\n– Source & Staging database should run in archive mode<\/p>\n

C) Asynchronous Hotlog CDC<\/strong> – In this method, online redo log file is used to capture changes and changes are captured at source database itself. Separate process mines redo logs and captures changes in change tables.<\/p>\n

D) Asynchronous Distributed Hotlog CDC<\/strong>– This method require staging database. Changes capture is performed by separate process on source database and then propagated to staging database and written to change tables (in staging database). For this method underlying infrastructure is provided by Oracle Streams.<\/p>\n

– Source & Staging database should run in archive mode<\/p>\n

<\/u><\/strong><\/p>\n

Related Documentation<\/u><\/strong><\/p>\n