Oracle Distributed Systems

Alternatives to Replication

Before moving on, I want to point out that there are alternatives to advanced replication. Like advanced replication, these alternatives can create replicas of table and data at remote sites. However, unlike advanced replication, they are not automatic.

A pplication- and Trigger-Based Replication

If you have a relatively simple replication requirement, you might consider replicating DML yourself, either by having your application perform writes to multiple databases or by including triggers on tables that perform remote DML. This is a “quick and dirty” solution and is practical only if very few objects are being replicated.

If you choose to create your own replication functionality, you will have to be sure to address issues such as failed writes to the remote databases and degraded performance if writes to many locations are required.

Export/Import

You can use Oracle’s export and import utilities to move data from one location to another. This is particularly useful if a large amount of data needs to be relocated, especially if the remote site(s) are available over a WAN or otherwise expensive network connection.

Of course, the disadvantages of the export/import utilities are that they are far from automated and are only point-in-time pictures of the database. In addition, changes you make to imported tables are not propagated back to the tables that were originally imported.

COPY/CREATE TABLE AS SELECT

You can use the SQL commands COPY or CREATE TABLE AS SELECT ...