About Materialized View Refresh

Refreshing a materialized view synchronizes data in the materialized view with data in its master table. The materialized view controls when the refresh is performed, either on a fixed schedule or on demand. During a refresh, row data from the master table is pulled down and applied at the materialized view site. Oracle Database provides the following refresh methods:

• Fast refresh pulls down only the rows that have changed since the last refresh.

• Complete refresh updates the entire materialized view.

• Force refresh performs a fast refresh when possible. When a fast refresh is not possible, force refresh performs a complete refresh.

A fast refresh is more efficient than a complete refresh. A fast refresh of a materialized view is possible only if the master table has a materialized view log. A materialized view log is a table at the master site that records all of the insert, update, and delete operations performed on the master table.

A materialized view log is associated with a single master table, and each master table has only one materialized view log, regardless of how many materialized views refresh from the master table. When a fast refresh is performed on a materialized view, entries in the materialized view log that have appeared since the materialized view was last refreshed are applied to the materialized view.