Oracle LDAP replication

1. Multi MasterOID replication uses database advanced replication feature
2. It uses asynchronous data propagation between supplier and consumer.
** Supplier writes changes to its change log and then send batched jobs to consumers, consumers receive change logs and applies the changes locally and then purges local changes data.

Figure on left hand side shows activity at supplier end and on right is consumer end.

All replica member in multimaster replication act as supplier and consumer at same time.

Replication process at Supplier end (Left Fig.)
1. User modify an entry in OID (Oracle LDAP Server)
2. The Oracle directory server generates a change log object in the change log object store.
3. At a scheduled time, the Oracle directory replication server launches an outbound change log processing thread. This thread translates the change log object into a row—for example, Change entry—in the change log table.
4. When a change entry is committed to the change log table, Advanced Replication immediately copies the change into the deferred transaction queue.
5. After a scheduled interval, Advanced Replication pushes pendingtransactions from the deferred transaction queue across the network to the consumer change log table.

Replication process at Consumer end (Right Fig.)

1. Change arrives in consumer change log table from supplier
2. The Oracle directory replication server launches a change log processing thread for each supplier, based on a scheduled replication cycle. This thread first consults the change status table for the last change applied from the supplier to the consumer.
3. The Oracle directory replication server then fetches and applies all the new changes from the change log table to the Oracle directory server.
4. The Oracle directory replication server then updates the change status table to record the last change applied from the supplier before exiting.
5. Advanced Replication copies the change status update into the deferred transaction queue.
6. After the scheduled Advanced Replication interval, Oracle Database Advanced Replication pushes pending change status updates from the deferred transaction queue to the supplier change status table.

원문 : http://becomeappsdba.blogspot.com/2007/03/multi-master-oid-replication.html