| Author: Vidhya 05 Sep 2008 | Member Level: Gold | Rating: Points: -20 |
hi,
.CDC - CAPTURING DATA CHANGE
.CDC is an oracle tool which can help to manage data changes and capture them in consistent manner with predefined APIs.
.CDC is not a development solution to perform any validations or transformation or provide any application specific checks etc.
.CDC doesn’t require any changes to the existing data model.
.CDC most commonly used to capture transactional changes from an OLTP system and publish the changes to one or more subscription systems.
.CDC purely worked based on logged operations, so any nonlogged DML operations are not captured.
.CDC doesn’t support direct load insert.
.CDC cannot be implemented on table with TDE (Transparent Data Encryption) enabled.
.Asynchronous mode capture wont work without supplemental logging.
Although direct select is possible on change table but the extraction of the changed data is valid/supported only via subscriber views.
Regards,
Vidhya
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| Author: http://dotnetvj.blogspot.com 05 Sep 2008 | Member Level: Diamond | Rating: Points: -20 |
Hi,
Oracle9i Database introduced the Change Data Capture (CDC) feature. CDC captures all the inserts, updates, and deletes made to user tables. These changes are stored in a database object called a change table, and the change data is made available to applications in a controlled way through what is called a subscriber view.
Prior to Oracle 10g, the change data was synchronously fed from the source. In Oracle Database 10g, it becomes possible to asynchronously feed the change data, and there are multiple options for how this feed is obtained and managed. Asynchronous data capture reads the changed data from Oracle redo log files. As a result of this, dependence on the transaction activity is avoided and performance overhead is reduced. Oracle Streams Methodology is used to capture change data from redo log files.
Asynchronous CDC requires a streams configuration for each CDC change set. These configurations include the streams capture and apply processes that read change data from redo log files and inserts it into CDC change tables.
Asynchronous CDC requires both the source and staging databases to be Oracle Database 10g.
Check out the below link for more information
http://www.praetoriate.com/10g_429.htm
Thanks -- Vj
http://dotnetvj.blogspot.com
Thanks -- Vj
http://dotnetvj.blogspot.com
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