Databases Reference
In-Depth Information
Considerations in setting up an asynchronous replication environment include the
following:
Tolerance for data divergence
The smaller the data divergence, the more individual replication actions will have
to be performed. You will reduce the resources needed to implement the replication
by increasing the data divergence.
Performance requirements
Since replication requires resources, frequent replication can have an impact on
performance.
Network bandwidth
Since replication uses network bandwidth, you have to consider the availability of
this resource.
Distance between sites
The more distance between sites, the longer the physical transfer of data will take.
Site and network stability
If a site or a network goes down, all replications that use that network or are destined
for that site will not be received. When either of these resources comes back online,
the stored replication traffic can have an impact on the amount of time it takes to
recover the site.
Experience level of your database administrators
Even the most effective replication plan can be undone by DBAs who aren't familiar
with replication.
While offering more flexibility, the added complexity and opportunity for data incon‐
sistencies generally cause organizations to avoid using asynchronous replication by itself
as part of a solution for unplanned downtime today and so GoldenGate is not on the
list of Oracle MAA recommendations. That said, GoldenGate is often used during
planned downtime for migrations and upgrades, and sometimes used in combination
with Active Data Guard or Real Application Clusters as part of an MAA strategy where
multimaster replication and other advanced replication techniques are desired.
Real Application Clusters and Instance Failures
Real Application Clusters (RAC) provides an Oracle-recommended MAA solution for
instance or computer failures. With RAC, the Oracle database is spread across multiple
nodes and each node has an active Oracle instance. Clients can connect to any of the
instances to access the same database.
