Updating oracle views

The complete refresh involves executing the query that defines the materialized view.This process can be slow, especially if the database must read and process huge amounts of data.Performing a refresh operation requires temporary space to rebuild the indexes and can require additional space for performing the refresh operation itself.Some sites might prefer not to refresh all of their materialized views at the same time: as soon as some underlying detail data has been updated, all materialized views using this data become stale.Materialized views can be refreshed either on demand or at regular time intervals.Alternatively, materialized views in the same database as their base tables can be refreshed whenever a transaction commits its changes to the base tables.Also adopting the out-of-place mechanism, a new refresh method called synchronous refresh is introduced in Oracle Database 12, Release 1.It targets the common usage scenario in the data warehouse where both fact tables and their materialized views are partitioned in the same way or their partitions are related by a functional dependency.

A materialized view log is a schema object that records changes to a base table so that a materialized view defined on the base table can be refreshed incrementally.If a row is rejected because of the CHECK OPTION, an error similar to the following is produced: ) and WITH CHECK OPTION is similar to a BLACKHOLE table: no row is ever inserted and no row is ever returned.An insertable view with a WHERE which is always false but no CHECK OPTION is a view that accepts data but does not show them.The PCT refresh method can be used if the modified base tables are partitioned and the modified base table partitions can be used to identify the affected partitions or portions of data in the materialized view.When there have been some partition maintenance operations on the base tables, this is the only incremental refresh method that can be used.

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