Database Reference
In-Depth Information
Figure 3.11
Master-to-Slave
versus Master-to-
Master Replication.
One of the most significant problems with the Oracle Replication
option is that it is often used inappropriately for backup and fail-over data-
bases. Oracle Replication has a level of complexity not suited to fail-over
and backup management.
Another method of replication for Oracle Database involves using Ora-
cle Streams and Oracle Advanced Queuing. A stream or pipe is established
between two databases, where a master database would have a capture
queue and a slave database an application queue. Oracle Streams Replica-
tion or Transparent Replication can include both master-to-master and
master-to-slave replication.
3.5.4
Standby Databases
Standby database architecture is shown in Figure 3.12. Standby or fail-
over databases can exist in two forms: a physical standby or a logical
standby. A logical standby is far more comprehensive and far more flexi-
ble. Physical standby is simple but much easier to implement and main-
tain than logical standby.
Both physical and logical standby databases can be configured for maxi-
mum safety or maximum performance. Redo log entries for maximum
