Monday, June 10, 2013

When to Replicate Data with Materialized Views

Unlike Oracle Streams replication, materialized views do not continuously replicate data at all times. A materialized view is a replica of a table or a subset of a table that can be refreshed to a transactionally consistent point in time. During a refresh, only the final values of the changed rows are pulled down and applied to the materialized view, no matter how many updates were applied to the master table. This reduces the amount of time that the remote site must be connected to the master site.
Materialized views are especially useful for locations with limited connectivity to the master site. Updatable materialized views allow these locations to function autonomously, even when connectivity is unavailable. When updates are allowed at multiple locations, ownership is typically partitioned in some manner between the locations to prevent conflicting updates. When conflicts are possible, Oracle provides conflict resolution methods that can resolve these conflicts automatically.
In addition to supporting disconnected computing, organizations can also use materialized views to improve performance and scalability by providing local access to data and by off loading processing at the primary location. For example, one or more materialized views might be used to off load reporting activity from an order-entry system.

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