This illustration shows the following process for row migration during propagation:
A user makes the following update to a table:
UPDATE hr.employees SET department_id=80 WHERE employee_id=190;
Before the update, the department_id
was 50
for the employee with employee_id
equal to 190
.
The source database records the change in the redo log.
A capture process captures the change and enqueues it as an LCR at the source database.
A propagation dequeues the LCR and transforms the UPDATE
into a DELETE
because the change satisfies a subset rule.
The propagation propagates the transformed LCR to a queue at the destination database.
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
.