Updatable Materialized Views

In a more advanced configuration, you can create an updatable materialized view that allows users to insert, update, and delete rows of the target master by performing these operations on the materialized view. An updatable materialized view may also contain a subset of the data in the target master.

Updatable materialized views are based on tables or other materialized views that have been set up to support replication. In fact, updatable materialized views must be part of a materialized view group that is based on another replication group.

Updatable materialized views have the following properties.

• They are always based on a single table, although multiple tables can be referenced in a subquery.

• They can be incrementally (or fast) refreshed.

• Oracle propagates the changes made to an updatable materialized view to the materialized view's remote master. The updates to the master then cascade to all other master sites.

Updatable materialized views provide the following benefits:

• Allow users to query and update a local replicated data set even when disconnected from the master.

• Require fewer resources than multimaster replication, while still supporting data updates. Materialized views can reduce the amount of stress placed on network resources because materialized views can be refreshed on demand, while multimaster replication propagates changes at regular intervals. In addition, because materialized views can reside in a database that contains far less data, the disk space and memory requirements for materialized view clients can be less than the requirements for an Oracle server containing master sites.