27
DBMS_LOGMNR_CDC_SUBSCRIBE

This chapter describes how to use the DBMS_LOGMNR_CDC_SUBSCRIBE package to view and query the change data that was captured and published with the DBMS_LOGMNR_CDC_PUBLISH package.

A Change Data Capture system usually has one publisher that captures and publishes changes for any number of Oracle source (relational) tables and many subscribers. The subscribers, typically applications, use the Oracle supplied package, DBMS_LOGMNR_CDC_SUBSCRIBE, to access the published data.

This chapter discusses the following topics:

• Subscribing to Change Data
• Summary of DBMS_LOGMNR_CDC_SUBSCRIBE Subprograms

Subscribing to Change Data

Once the publisher sets up the system to capture data into change tables and grants access, subscribers can access and query the published change data for any of the source tables of interest. Using the procedures in the DBMS_LOGMNR_CDC_SUBSCRIBE package, the subscriber accomplishes the following main objectives:

1. Indicate the change data of interest by creating subscriptions to published source tables and source columns.
2. Extend the subscription window and create a new subscriber view when the subscriber is ready to receive a set of change data.
3. Use SELECT statements to retrieve change data from the subscriber views.
4. Drop the subscriber view and purge the subscription window when finished processing a block of changes.
5. Drop the subscription when the subscriber no longer needs its change data.