Illustration strms040.gif shows the following process for row migration during propagation:

  1. A user makes the following update to a table:

    UPDATE hr.employees SET department_id=80 WHERE employee_id=190;
  2. Before the update, the department_id was 50 for the employee with employee_id equal to 190.

  3. The source database records the change in the redo log.

  4. A capture process captures the change and enqueues it as an LCR into a queue at the source database.

  5. A propagation dequeues the LCR and transforms the UPDATE into a DELETE because the change satisfies a subset rule.

  6. The propagation propagates the transformed LCR to a queue at the destination database.

  7. An apply process dequeues the change and applies it as a DELETE from an hr.employees subset table. This subset table contains rows only for employees with a department_id equal to 50.