Since when we are woring with various databases running in different system So sometime we may needed to fetch some records from the remote location so it may quit expensive in terms of resourse of fetching data directly from remote location.To to minimize to response time and to increse the throughput we may create the copy to that on local database by using data from remote database.This duplicate copy is Known as materialised view which may be refreshed as per as requirment as option avilable with oracle such as fast complete and refresh.
Materialized View stores both - definition of the view and rows resulted from execution of the viewMain disadvantage of materialized view is that its contents get outdated when underlying base table is modified .U can refresh Materialized View using DBMS_MVIEW.REFRESH
Materialised view contain data of last refesh database but incase of view it stores only complex sql statement. Whenever your refresh the database the data will update on the materialised view so its very quick to retrieve data.
A materialized view (MV) is similar to a view but the data is actually stored on disk (view that materializes). Materialized views are often used for summary and pre-joined tables or just to make a snapshot of a table available on a remote system. A MV must be refreshed when the data in the underlying tables is changed.
