Event Generation
The Oracle CDC Client origin can generate events that you can use in an event stream when the origin uses redo logs as the dictionary source. The origin does not generate events when using the online catalog as the dictionary source.
When you use redo logs as the dictionary source and enable event generation, the Oracle CDC Client generates events when it reads DDL statements. It generates events for ALTER, CREATE, DROP, and TRUNCATE statements.
When you start the pipeline, the origin queries the database and caches the schemas for all tables listed in the origin, and then generates an initial event record for each table. Each event record describes the current schema for each table. The origin uses the cached schemas to generate records when processing data-related redo log entries.
The origin then generates an event record for each DDL statement it encounters in the redo logs. Each event record includes the DDL statement and the related table in record header attributes.
The origin includes table schema information in the event record for new and updated tables. When the origin encounters an ALTER or CREATE statement, it queries the database for the latest schema for the table.
If the ALTER statement is an update to a cached schema, the origin updates the cache and includes the updated table schema in the event record. If the ALTER statement is older than the cached schema, the origin does not include the table schema in the event record. Similarly, if the CREATE statement is for a "new" table, the origin caches the new table and includes the table schema in the event record. Because the origin verifies that all specified tables exist when the pipeline starts, this can occur only when the table is dropped and created after the pipeline starts. If the CREATE statement is for a table that is already cached, the origin does not include the table schema in the event record.
- With the Email executor to send a custom email
after receiving an event.
For an example, see Sending Email During Pipeline Processing.
- With a destination to store event information.
For an example, see Preserving an Audit Trail of Events.
For more information about dataflow triggers and the event framework, see Dataflow Triggers Overview.