Materialized view questions...

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• Materialized view Questions PLZ HELP!

  Hi all
  
  How to check the time required for a materialized view to run at a given time.
  My point of view materialized is a full refresh that runs automatically at 03:00.
  
  (a) I interviewed dba_jobs and dba_mview_refresh_times and matched the last_date and last_refresh to find the total time. How can I know that 80 JOBS matches my opinion MVIEW_UNION in a much easier way?
  
  SQL > select job, last_date, order dba_jobs total_time in last_date;
  WORK LAST_DATE TOTAL_TIME
  ---------- ----------------- ----------
  80 05/05/10 03:00:02 5255
  
  SQL > select name, last_refresh from dba_mview_refresh_times where owner
  NAME LAST_REFRESH
  ------------------------------ -----------------
  MVIEW_UNION 05/05/10 03:00:02
  
  
  
  (b) also is total_time time it took the request to run today at 03:00, that is to say he started at 03:00 and ended at all about 4:45(3+5255_msec) or is it the time it has taken since the day wherever it has been planned in dba_jobs (IE back of 1 week)
  
  (c) also my dosent table source contain all indexes and I created indexes on the materialized view, I want to know if the full update will recreate the indxes.
  
  Thanks in advance,
  Kind regards

  Index on the MV are independent of indexes on the tables in the source.

  The "container" for a MV is a table. Therefore, indexes can be created on this topic.
  A FULL refreshment made with ATOMIC_REFRESH set to FALSE would be a TRUNCATE and INSERT APPEND. The index may be updated at the end.
  A FULL refreshment made with ATOMIC_REFRESH set to TRUE would be a DELETE and INSERT. This, as it is, has notable requirements of Undo (and redo). Index, if any, would also add many more requirements Undo (and redo) and updating.
  A QUICK update is an UPDATE or INSERT. Again, the presence of indexes can have an impact. If the discount is small (ie. the proportion of the updates/news lines is low compared with the lines already present in the MV), then the index can be kept because they are (the overhead of recreating the index i would exceed overload time and undo/redo of the DML with the present indices). However, if the QUICK updates/inserts many rows update, a strategy of DROP and CREATE better index.

  Hemant K Collette
  http://hemantoracledba.blogspot.com

• Materialized view - Alter

  Hello gurus,
  
  
  How to alter a materialized view question him with out droping? give me a small example
  
  
  
  
  Kind regards
  A friend :)

  You reference 10.1 documentation. Please see the latest version 11.2

  A MV query cannot be changed. The MV should be deleted and rebuilt.
  (think about it... How do you change a MV as the query on what is built is changed and/or columns are added/removed)?

  The documentation that you reference says:
  Use the ALTER MATERIALIZED VIEW statement to alter a materialized view existing in one or more of the following ways:

  To change its storage features

  To change its refresh, mode or time method

  To change its structure to make it another type of materialized view

  To enable or disable the query rewriting.

  Hemant K Collette

• Question of materialized view

  Hello
  EBS version 11.5.10.2
  
  I would like to know if the next materialized view is used by default EBS, or if it was built by one of our developers.
  Thank you
  

  select  OWNER , NAME , MASTER_OWNER , MASTER 
       from  dba_snapshot_refresh_times
       where TRUNC(last_refresh) = '13-MAR-11';
  
  OWNER      NAME                           MASTER_OWN MASTER
  ---------- ------------------------------ ---------- --------------------------------------------------
  APPS       CUST_CREDIT_MV                 AR         AR_PAYMENT_SCHEDULES_ALL

  I checked two 11.5.10 facilities. I can't find this mv. This is very probably a custom.

  Hope that answers your question,
  Sandeep Gandhi

• Questions on the tables of materialized views and MV newspaper

  Hi all
  
  Have some questions about Materialized View.
  
  (1) once the materialized view reads the records from the table MLOG, reviews the MLOG get purged. fix? or is that not the case? In some cases, I see still (old) records in the MLOG table even after updating MV.
  
  (2) how the table MLOG distinguishes between a reading which comes from a MV and a reading that comes from a user? If I execute manually
  "Select * < table MLOG > ' could get record of the table MLOG redacted all the same way as it does after a refresh of MV?
  
  (3) one of our MV updates crashes intermittently. Based on the events of waiting I noticed that it was a 'db file sequential read' against the main table. Finally I had to put an end to the update. I don't know why it was sequential reading on the main table when she should be reading the table MLOG. Any ideas?
  
  (4) I saw 'file db scattered read' (full table scan) usually on tables, but I was surprised to see 'db file sequential read' against the table. I thought sequential read occurs normally against the index. All the world has noticed this behavior?
  
  Thanks for your time.

  (1) once all the registered materialized views have read a particular line in a trunk of materialized view, it is removed, Yes. If there are multiple materialized views that are based on the same newspaper, they would all need to refresh before it would be safe to delete the log entry for MV. If one of the materialized views is no incremental updating, there may be cases where the log purge automatically.

  (2) No, your query does not cause anything be served (although you wouldn't see something interesting unless you get to implement a lot of code to analyze change vectors stored in the journal). I don't know the exact mechanism used by Oracle has been published, if you could go through and draw a session to get an idea of the moving parts. From a practical point of view, you just need to know that when you create an updatable materialized view fast, it will register as interested especially newspapers MV.

  (3) it depends on what is stored in the log of MV. The update process may need to recover specific table columns if your log stores just the fact that the data for a particular key changed. You can specify when you create a materialized view that you want to store specific columns or include the new clause values (with the NEW VALUES INCLUDING). It is perhaps beneficial (or necessary) for the refreshment quick process, but it would tend to increase the storage space for the materialized view log and increase the cost of the maintianing the materialized view log.

  (4) sequential reads on a table are perfectly normal - it just means that someone looking for a block of data in the table (i.e. looking a line in the table of ROWID based on the ROWID in an index or a materialized view log).

  Justin

• question on the materialized view unregistered on the main site

  Hello
  
  you know how one knows, on the main site, on the existence of a materialized view another site referring to other tables to a primary site. It seems registration is not required.
  
  the site main orcl1: I have a table, and a materialized view log defined on A table.
  another site orcl2: have a link db orcl1 and rapid updatable view SCOTT materialized. A_MVW (create a materialized view A_MVW cool off quickly in select * from A@orcl1)
  
  on orcl1 I perform: exec DBMS_MVIEW. UNREGISTER_MVIEW (mviewowner = > 'SCOTT', mviewname = > mviewsite, 'A_MVW' = > 'ORCL2');
  so the materialized view seems to be correctly set aside (because it no longer appears in: select * from DBA_REGISTERED_MVIEWS ;))
  But, to my surprise, I can still perform refreshes fast on A_MVW, which also remove rows from the materialized view log. So how is site orcl1 always aware of the existence of the materialized view?
  
  It seems that, registered or not to the main site, a materialized view has the same... or is not? where is it stored, on the main site, information about materialized views (especially those of quickly updatable) as local tables reffer?
  
  Thank you

  See DocIDs 258634.1, 67371.1, 1031924.6
  on Oracle's Support website.

  Hemant K Collette

• question on MATERIALIZED VIEW and table

  Hello
  
  There is table (name is test123) and MATERIALIZED VIEW (the name is also test123) stored in the same pattern (the name is schema123).
  
  If I run sql: Select in schema123.test123; *
  
  I want to know the result I get data data table test123 or MATERIALIZED VIEW test123, which one of them?
  
  Thanks in advance!

  Hi Tao2,

  You will get the data in the table.

  Kind regards
  oraclekt

• Question about the materialized view

  I read that Materialized Views should not be used to select the data. I thought that the whole purpose of materialized view to pre-computes joins and aggregation, so that we can recover more quickly. Please let me know your point of view. I'm working on a project of storage and using materialized in the queue views and data reports

  user637544 wrote:
  I read that Materialized Views should not be used to select the data.

  Where did you read that? As stone and others have tried to indicate, this is not the case. Note that the Data Warehousing Guide Peter links has several chapters on materialized views and their uses. Precomputing of aggregates is certainly one of these uses.

  Justin

• What is the best way to change a column type in the materialized view?

  Hello my dear friends,.

  I want to change a column type in a materialized view. VARCHAR2 NUMBER, so what do you recommend? What is the best way to do it?

  Thank you

  You can not change the data type of the column while there are data in the MV, so you might as well give up and recreate the MV with a TO_CHAR() around the column in question in the application of MV to get the data exactly as you want (be sure to include an appropriate format mask). That said, I'm fighting to think reasonable grounds to make such a change.

• Materialized views Refresh method and refresh option

  Hi Experts,

  According to the docs, If the MV contains the following, MV is considered complex. I wonder is there any view data dictionary that indicates the type of MV? Because is very easy to the candidate a complex type mv. Because many queries contains the properties below.

  http://docs.Oracle.com/CD/B28359_01/server.111/b28326/repmview.htm#i52501

  http://docs.Oracle.com/CD/B28359_01/server.111/b28313/basicmv.htm

  Specifically, a materialized view is considered complex if the materialized view definition query contains:

  • A CONNECT BY clause
  • An INTERSECT , MINUS , or UNION ALL operation
  • he DISTINCT or UNIQUE keyword
  • In some cases, an aggregate function, although it is possible to have an aggregation function in the query definition and always have a simple materialized view
  • In some cases, joins other than those in a subquery, although it is possible to have joins in the definition to interrogate and still have a simple materialized view
  • In some cases, a UNION operation

  
  

  After that I kept going to read that I learned that when a VM is created, the refresh mode is specified according to the type of the MV. That means, using ON-DEMAND refresh mode is widespread. The documentation mentions that there isa also refresh option. My question is, is it possible to specify

  ON REQUEST and FAST together?

  Also, what are the differences between FULL and FAST. Ends truncate the table and fill it up again?

  ON COMMIT

  Refresh product automatically when a transaction which changed one of the paintings of the materialized view's retail is committed. This can be specified as the materialized view is quickly updatable (in other words, not complex). The ON COMMIT privilege is required to use this mode.

  ON DEMAND

  Refresh occurs when a user manually executes one of the procedures available refresh contained in the DBMS_MVIEW package ( REFRESH , REFRESH_ALL_MVIEWS , REFRESH_DEPENDENT ).

  COMPLETE	Refreshes and recalculating the materialized view query definition.
  FAST	Applies incremental changes to refresh the materialized view using the information recorded in the papers of the materialized view, or an SQL * Loader direct-path access or a partition maintenance operation.

  FORCE

  Applies FAST update if possible; otherwise, it applies COMPLETE Refresh.

  NEVER

  Indicates that the materialized view will not be updated with updating mechanisms.

  Select * from version of v$.

  Oracle Database 11 g Release 11.2.0.4.0 - 64 bit Production

  Thank you

  Çaglar wrote:

  ...

  Also, what are the differences between FULL and FAST. Ends truncate the table and fill it up again?

  ...

  Thank you

  I just want to answer the truncated question. Seems that nobody covered that yet.

  Answer: It depends.

  If you do a full refresh, then the default is to use ATOMIC_REFRESH = TRUE.

  This means that the update is done via an insert, delete , and ... Select.

  You can change it to ATOMIC_REFRESH = FALSE (parameter dbms_mview.refresh).

  This means that is a TRUNCATE and insert a ... Select with APPEND peak (path direct insert).

  Refresh if Atomic = FALSE is considerably faster than the default. Also way less Archives of newspapers are written.

  The downside is however that, during the update the MV is empty, is no longer an atomar operation!

  See also Oracle documentation: http://docs.oracle.com/cd/B28359_01/appdev.111/b28419/d_mview.htm#i997194

• Problem with a complete refresh materialized view when using rownum

  Hi all

  I had a problem with rownum when complete using Refresh

  I use rownum when you create the materialized view, and this is the generation properly. But the question was when I even refreshing, rownum was not get sorted in ascending order.

  anyone encountered this scenario

  rownum is determined as the line came out, also "order by rownum" does absolutely nothing.

  http://docs.Oracle.com/CD/B19306_01/server.102/b14200/pseudocolumns009.htm

• effect of pump or etl data on the materialized view logs

  Hi, we are mobile/upgrading an instance of 10g to 12 c, where one materialized view logs and expect to do one of the following:

  (1) extract/import the meta, only using data pump data and move data using an etl tool

  (2) comprehensive database extract/import using the data pump in

  are there questions that we must be aware of when the displacement of these with either scenario materialized view logs?

  Thanks for any information you can provide.

  > are there questions that we should be aware of when the displacement of these materialized view logs with either scenario?

  No problem

• Materialized view automatically refresh? If the updating of the means how?

  Materialized view refresh automatically? If the updating of the means how?

  It is expected is not to ask questions of the basic documentation.

  Refresh Options

  When you define a materialized view, you can specify three update options: how to refresh, what kind of update and can trust constraints be used. If not specified, default values are considered as ON DEMAND , FORCE , and ENFORCED forced respectively.

  The two execution modes are ON COMMIT and ON DEMAND . According to the materialized view, you create, some options may be unavailable. Update modes are described in table 8-4 .

  Table 8-4 Modes of discount

  Refresh the Mode	Description
  ON COMMIT	Refresh product automatically when a transaction which changed one of the paintings of the materialized view's retail is committed. This can be specified as the materialized view is quickly updatable (in other words, no complex). The ON COMMIT privilege is required to use this mode.
  ON DEMAND	Refresh occurs when a user manually executes one of the procedures available refresh contained in the DBMS_MVIEW package ( REFRESH , REFRESH_ALL_MVIEWS , REFRESH_DEPENDENT ).

  http://docs.Oracle.com/CD/B28359_01/server.111/b28313/basicmv.htm#i1006193

• Difference between the table and Materialized View

  Is there an advantage outside automatic synchronization (founded refresh selected type) using Materialized View?

  I came across this question as table and MV both store values, and we can also update table using the code what is the need of MV? Why not create a table instead of MV with the same definition and same charly?

  I need some explanation to force someone to convince himself.

  Thank you

  http://docs.Oracle.com/CD/B19306_01/server.102/b14223/basicmv.htm

  Sections that highlight its strengths:

  1. materialized views for data warehouses

  2. materialized views for distributed computing

  Query, re - write, features as Materialized view log files that can be used for replication between databases, etc...

• Materialized view: when to use a full refresh

  Thank you in advance, I read in the book of the Oracle University - "a complete refresh of a materialized view is to truncate the existing data and reinsert all data based on detail tables, re-running the query definition to CREATE order. Quick updates apply only changes since the last update. My question is what we need to complete refresh because the data in the table created for the two methods are ultimately the same and fast refresh is more "quickly"?

  Well, I don't know about the Oracle University book, but Oracle manual list a long list of restrictions when fast updating is not possible. I hope that answers your question.

  SY.