This process is called incremental or fast refresh. This is the fastest way I could find, please let me know if anyone else has any ideas. CREATE/ALTER/DROP MATERIALIZED VIEW LOG : CREATE MATERIALIZED VIEW LOG ON [schema. Specify the refresh method for which a materialized view log will be used. However, indexes created on the container table automatically during creation of the materialized view are preserved, with one exception: the index created during the creation of a rowid materialized view is dropped. select count (*) from mlog$_MyTable; Get the list of all materialized views on a view log. In contrary of views, materialized views avoid executing the SQL query for every access by storing the result set of the query. look at the object_type in user_objects to be certain. Oracle Database uses these objects to maintain the materialized view data. Setting materialized view log parameters. Get Oracle SQL: the Essential Reference now with O’Reilly online learning. We are using Discoverer with a 9i Database in Archivelog mode. When you drop a materialized view, Oracle Database does not place it in the recycle bin. When a materialized view is created Oracle may add system generated indexes to its underlying table (i.e. 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. Performing CPU-intensive calculations 4. Question: What is the script to get the DDL for a materialized view. Oracle provides the means by which you can group related views together. You can see that I’ve added the sequence, that was not mentioned by the explain_mview. O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers. All these internal queries are related to new feature of Oracle 12.2 which is related to materialized view usage tracking. There's an entry in dba_summaries for the MV. Alternatively, you can drop a materialized view using Oracle Enterprise Manager. SQL> drop materialized view log on DEMO; Materialized view log dropped. The process of dropping a column from a big table can be time and resource consuming. I’ll come back on that later and probably in another post. Start your free trial. Oracle supplies the DBMS_REFRESH package with the following procedures; MAKE: Make a Refresh Group: ADD: Add materialized view to the refresh group: SUBTRACT: Remove materialized view from the refresh group: REFRESH: Manually refresh the group: CHANGE: … the table containing the results of the query, not to be confused with a base table). You can specify synchronous refresh, which is introduced in Oracle Database 12 c, or fast refresh, which is also available in earlier releases. Get Oracle SQL: the Essential Reference now with O’Reilly online learning. Posted by Apun Hiran at 12:47 AM Labels: drop mview, materialized view, oracle. Therefore, you cannot subsequently either purge or undrop the materialized view. ]materialized_view_name [Physical_Attributes_Clause] [TABLESPACE tablespace] [STORAGE … Materialized views are a really useful performance feature, allowing you to pre-calcuate joins and aggregations, which can make applications and reports feel more responsive. These MVs themselves are marked as INVALID. To determine view dependencies before dropping a materialized view, use the sa_dependent_views system procedure. Get latest refresh times for all materialized views. Fast refreshes allow you to run refreshes more often, and in some cases you can make use of refreshes triggered on commit of changes to the base tables, but this can represent a significant overhe… The materialized view must be in your own schema or you must have the DROP ANY MATERIALIZED VIEW system privilege. table . I've been trying to DROP an MV which is defined as REFRESH ON DEMAND and there are no locks anywhere. In this section, you learn about the following uses of these views, as they are applicable to the topic of large databases. 4 Comments: Ritzy said... You may find the following Metalink Link pretty useful as well. You cannot execute a DROP MATERIALIZED VIEW statement on an object that is currently being used by another connection. A DROP statement sits there and never returns. A materialized view is a database object that contains the results of a query. I have a materialized view that's fast refreshable, joining two tables. Can not Drop Materialized View on 12c and above? Originally called snapshots, materialized views were introduced in Oracle8i and are only available in the Enterprise Edition. after a quick search, I learned that those are new tables which came with 12c and above. 3) CASCADE CONSTRAINT Third, if a view has any constraint, you must specify the CASCADE CONSTRAINT clause to drop all referential integrity constraints that refer to primary key and unique keys in the view. DROP MATERIALIZED VIEW sales_sum_mv; This statement drops the materialized view sales_sum_mv. This note describes how Oracle 12c now gives you an official way of doing something similar - the "out of place" refresh. Re: Unable to drop materialized view 161380 Apr 1, 2003 12:09 PM ( in response to 177367 ) perhaps you made the view as a normal view rather than a materialized view. alter materialized view view_name refresh on demand; This seems fairly clear in the documentation . Use the DROP MATERIALIZED VIEW statement to remove an existing materialized view from the database. During this heavy hardworking, I faced with a problem on one of my customers. 12c MView refresh Filed under: 12c,Infrastructure,Materialized view,Oracle — Jonathan Lewis @ 1:19 pm GMT Mar 26,2015 . March 26, 2015. You must have the privileges necessary to create these objects. Get DDL for Materialized View Script. If you drop a materialized view, then any compiled requests that were rewritten to use the materialized view will be invalidated and recompiled automatically. But recompiling them never returns. Oracle stores some statistical information on them by default but they have no indexes and when you tried to drop an MV oracle try to delete those tables for that MV but because lack of indexes (probably) it gets an internal timeout. When running a DROP MATERIALIZED VIEW the session hangs.The hang has been reproduced and this time we have some trace files generated:Connect to any session and run the following commands: This wait event was determined to be due to a DBMS_JOB entry to refresh the mview we are trying to drop.  So after removing this job we could then successfully drop the mview. Therefore, you cannot subsequently either purge or undrop the materialized view. When I try to drop either the MV itself or logs associated with constituent tables, it starts the process but never comes back. Executing a DROP MATERIALIZED VIEW statement changes the status of all dependent regular views to INVALID. Online training, plus books, videos, and digital content from 200+ publishers a Database! Based on one SOURCE table it in the Enterprise Edition dbms_metadata for extracting the materialized view, Oracle can the... Which you can see that I ’ ll come back on that later and probably in another post materialized... 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