Materialized view based replication is very useful when the changes at the master site do not have to be immediately available at the secondary sites. This is also useful when the connectivity between the master and slave sites is not continuous. When only a subset of tables or portions of the tables are required at the secondary sites in an asynchronous fashion, materialized view based replication is one of the most common ways to achieve it.
As we discussed in the previous chapter, a materialized view is a replica of a table that can be refreshed at regular intervals or on demand. During a refresh, only the final values of the changed rows are pulled down, no matter how many updates were applied to the master table. This results in the reduced amount of data being transferred to the remote site.
Let's use the
LAND_PARCELS table in our example to show the replication process using the materialized views. First, the database administrators at the city...