Description of the illustration strms040.eps

This illustration 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 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.