Create materialized view on demand refresh example

When creating a materialized view , you have the option of specifying whether the refresh occurs ON DEMAND or ON COMMIT. If you anticipate performing insert, update or delete operations on tables referenced by a materialized view concurrently with the refresh of that materialized view , and that materialized view includes joins and aggregation, Oracle. By default, Oracle Database creates a primary key materialized view with refresh on demand only.

If a materialized view log exists on employees, then mvcan be altered to be capable of fast refresh. If no such log exists, then only full refresh of mvis possible.

Up to this point in the tutorial we have always refreshed our materialized views manually with the DBMS_MVIEW. Oracle Database can use this materialized view log to perform fast refreshes for all fast-refreshable materialized views based on the master table. To fast refresh a materialized join view , you must create a materialized view log for each of the tables referenced by the materialized views. Below is an example of an Oracle materialized view with an ON COMMIT refresh. Home Articles Misc Here.

FROM emp e, dept d WHERE e. F or example , can I create a COMPLEX TYPE materialized view with ON DEMAND and FAST together?

Materialized Views in Oracle. However, these options seem independent from each other. One is REFRESH MODE, the other is REFRESH OPTION. It indicates that the materialized view will be refreshed on demand by calling one of the three DBMS_MVIEW refresh procedures.

CREATE MATERIALIZED VIEW LOG ON SCOTT. ON COMMIT indicates that a fast refresh is to occur whenever the database commits a transaction that operates on a master table. When a materialized view is maintained using the ON COMMIT metho the time required to complete the commit may be slightly longer than usual. Because the materialized view conforms to the conditions for fast refresh , the database will perform a fast refresh. REFRESH FAST: uses an incremental refresh method which uses changes made to the underlying tables in a log file.

The next example examines the behavior of REFRESH ON COMMIT without a specified refresh method. HINT: Create a unique index with no WHERE clause on one or more columns of the materialized view. To be able to REFRESH the materialized view we need to add a unique index.

Add the unique index to the materialized view with the following script. A grouping of materialized views so that they can be refreshed as a single transaction for consistency. Refresh Log: When DML changes are made to master table data, Oracle Database stores rows describing those changes in the materialized view log and then uses the materialized view log to refresh materialized views based on the master table.

Without a materialized view log, Oracle Database must re-execute the materialized view query to refresh the materialized view.

Usually, a fast refresh takes less time than a complete refresh. In the example , the function takes a date parameter to only update monthly sales information starting from a particular date. A materialized view log is located in the master database in the same schema as the master table.

Meaning that if you drop Mview, your table will also be dropped (unless you use “preserve table” clause). But if its a prebuilt table, table will not be dropped even if you drop MView. I am not able to find the right documentation on setting specific timings for materialized view refresh for oracle.

This way you can retain data.