The DBA_MVREF_CHANGE_STATS view stores detailed change data statistics for materialized view refresh operations. Example 7-7 Refreshing a Materialized View that is Based on a Hybrid Partitioned Table. To get this information, query [ DBA / ALL / USER ]_OBJECTS depending on your privileges: DBA_OBJECTS : All objects in the database When creating a materialized view, you have the option of specifying whether the refresh occurs ON DEMAND or ON COMMIT. For example, try to avoid the following: If many updates are needed, try to group them all into one transaction because refresh is performed just once at commit time, rather than after each update. You can use fast refresh with a mixture of conventional DML and direct loads. For example, when the REFRESH_DEPENDENT procedure is used to refresh a single materialized view, all materialized views that are dependent on the specified materialized view are also refreshed as part of the same refresh operation. Each procedure contains different parameters that specify how the refresh must be performed. In some situations, you might not want to drop the old data immediately, but keep it as part of the partitioned table; although the data is no longer of main interest, there are still potential queries accessing this old, read-only data. Use INSERT to add the new data to an existing partition. CREATE VIEW dbo.vw_View AS SELECT ID = 1 GO CREATE PROCEDURE dbo.usp_Procedure AS BEGIN SELECT ID FROM dbo.vw_View END GO ALTER VIEW dbo.vw_View AS SELECT New_ID = 1 GO We will get an error while executing the storage procedure: Msg 207, Level 16, State 1, Procedure usp_Procedure, Line 6 Invalid column name 'ID'. Suppose that a retail company has previously sold products from XYZ Software, and that XYZ Software has subsequently gone out of business. PCT refresh provides a very efficient mechanism to maintain the materialized view in this case. The partition exchange in out-of-place PCT refresh impacts the global index on the materialized view. To modify the collection level for materialized view refresh statistics, either at the database level or materialized view level: Example 9-3 Setting the Materialized View Statistics Collection Level for the Entire Database. This includes referential integrity constraints. All underlying objects are treated as ordinary tables when refreshing materialized views. Note that the retention period set for SALES_MV remains unaltered. For local materialized views, it chooses the refresh method which is estimated by optimizer to be most efficient. Each of these materialized views gets rewritten against the one prior to it in the list). However, sometimes other data might need to be removed from a data warehouse. Can anybody help? Use the procedures in the DBMS_MVIEW_STATS package to set the COLLECTION_LEVEL parameter, which specifies the collection level for materialized view refresh statistics. Share Improve this answer Follow edited Jan 9, 2018 at 12:50 answered Jan 9, 2018 at 12:31 SQL> SQL> create materialized view log on t with primary key; Materialized view log created. -- Use below to Check Materialized Views Refresh Timing in Oracle Database : COLUMN job format 9999 COLUMN mview_name format a50 wrap heading "Mview|Name" COLUMN last_run format a20 COLUMN next_run format a20 COLUMN interval format a20 SET pages 56 lines 130 feedback on echo off long 1000000 TTITLE 'Refresh Times of MViews' SELECT job, what Home Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Fast refresh will automatically detect that PCT is available and perform a PCT refresh. When designing the entire data warehouse load process, it was determined that the new_sales table would contain records with the following semantics: If a given sales_transaction_id of a record in new_sales already exists in sales, then update the sales table by adding the sales_dollar_amount and sales_quantity_sold values from the new_sales table to the existing row in the sales table. This example sets the retention period for materialized view refresh statistics to -1 thereby ensuring that refresh statistics are not automatically purged when the default retention period is reached. Asking for help, clarification, or responding to other answers. Oracle Database stores materialized view refresh statistics in the data dictionary. A complete refresh occurs when the materialized view is initially created when it is defined as BUILD IMMEDIATE, unless the materialized view references a prebuilt table or is defined as BUILD DEFERRED. For local materialized views, it chooses the refresh method which is estimated by optimizer to be most efficient. You can modify the statistics collection behavior either for the entire database or for one or more materialized views. More info here: How to Refresh a Materialized View in Parallel. In the case of full refresh, this requires temporary sort space to rebuild all indexes during refresh. Example 7-14 Unconditional Inserts with MERGE Statements. The out-of-place refresh creates one or more outside tables and executes the refresh statements on the outside tables and then switches the materialized view or affected materialized view partitions with the outside tables. Refer to View live queries with pg_stat_activity to analyze live queries. To analyze the refresh and rewrite capabilities of a potential materialized view, you perform the following steps: 1. It only takes a minute to sign up. Detailed current and historical statistics can be used to quickly analyze the performance of materialized view refresh operations. Apply additional WHERE conditions for the UPDATE or INSERT portion of the MERGE statement. The partition, year_2001, was not refreshed as it was already fresh. You may want to cleanse tables while populating or updating them. You can refresh your materialized views fast after partition maintenance operations on the detail tables. Example 7-13 Using the DELETE Clause with MERGE Statements. The rest compiled fine for me although I haven't called the procedure from code yet. First, you can physically delete all data from the database by dropping the partition containing the old data, thus freeing the allocated space: Also, you can exchange the old partition with an empty table of the same structure; this empty table is created equivalent to steps 1 and 2 described in the load process. If the refresh fails for any of the materialized views, none of the materialized views are updated. Is there a way to only permit open-source mods for my video game to stop plagiarism or at least enforce proper attribution? The refresh methods considered are log-based FAST and FAST_PCT. CREATE MATERIALIZED VIEW store_sales_mv PCTFREE 0 TABLESPACE mviews STORAGE (INITIAL 16k NEXT 16k PCTINCREASE 0) PARALLEL BUILD DEFERRED REFRESH COMPLETE ENABLE QUERY REWRITE AS SELECT s.store_name, SUM(dollar_sales) AS sum . Real-world data warehouse refresh characteristics are always more complex. Just as a new partition can be added to the sales table (as described earlier), an old partition can be quickly (and independently) removed from the sales table. You can use the complete, fast, or PCT refresh methods to refresh a materialized view that is based on a hybrid partitioned table. Torsion-free virtually free-by-cyclic groups. If there were only foreign-key constraints, the exchange operation would be instantaneous. The term MVIEW will be used to refer tomaterialized view throughout this article. In fact, the load process is often the primary consideration in choosing the partitioning scheme of data warehouse tables and indexes. To view detailed refresh statistics for materialized view refresh operations: Example 9-15 Listing All Materialized Views Refreshed in a Single Refresh Operation. You can skip refreshing materialized view data that corresponds to external partitions by using the skip_ext_data attribute in the DBMS_MVIEW.REFRESH procedure. Contains information related to each refresh statement that is part of a single materialized view refresh operation. Avoid mixing deletes and direct loads. A very common scenario is the rolling window discussed previously, in which older data is rolled out of the data warehouse to make room for new data. Example 9-14 Displaying Materialized Views Based on their Refresh Times. If that is not possible, restrict the conventional DML to the table to inserts only, to get much better refresh performance. After the first compressed partition is added, no additional actions are necessary for all subsequent operations involving compressed partitions. and out_of_place = true, out-of-place fast refresh are attempted first, then out-of-place PCT refresh, and finally out-of-place complete refresh. Statistics can be collected for all materialized views in the database or for a specific set of materialized views. It may be required to increase the frequency of the refresh so as to have less changes in a refresh, The other thing to check the master table. When a materialized view is refreshed in atomic mode, it is eligible for query rewrite if the rewrite integrity mode is set to stale_tolerated. This example sets the collection level for the materialized view SALES_MV in the SH schema to TYPICAL. Oracle - What happens when refreshing a 'REFRESH FORCE ON DEMAND' view with DBMS_MVIEW.REFRESH. With 12c Release 1, a new refresh option is available to improve materialized view refresh performance and availability. Therefore, do not perform direct-path INSERT and DML to other tables in the same transaction, as Oracle may not be able to optimize the refresh phase. Set the number of job queue processes greater than the number of processors. or with more complex disjunct where conditions), using e.g. When there have been some partition maintenance operations on the base tables, this is the only incremental refresh method that can be used. Create the materialized view. In most cases, this can be neglected, because this part of the partitioned table should not be accessed too often. If you are not sure how to make a materialized view fast refreshable, you can use the DBMS_ADVISOR.TUNE_MVIEW procedure, which provides a script containing the statements required to create a fast refreshable materialized view. Using a single INSERT statement (which can be parallelized), the product table can be altered to reflect the new products: Occasionally, it is necessary to remove large amounts of data from a data warehouse. To learn more, see our tips on writing great answers. To look at the progress of which jobs are on which queue, use: Three views are provided for checking the status of a materialized view: DBA_MVIEWS, ALL_MVIEWS, and USER_MVIEWS. This gives Oracle an opportunity to schedule refresh of all the materialized views in the right order taking into account dependencies imposed by nested materialized views and potential for efficient refresh by using query rewrite against other materialized views. 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