Replication :: Materialized Views Refresh In Snapshot-group?
Mar 24, 2010
How to refresh the dependent materialized views in a snapshot group. It refreshes in the order we add the materialized views to snapshot group?
Here below is the scenario.
MATVW_A
CREATE MATERIALIZED VIEW MATVW_A BUILD IMMEDIATE
REFRESH FAST ON COMMIT
AS SELECT * FROM EMP;
MATVW_B
CREATE MATERIALIZED VIEW MATVW_B BUILD IMMEDIATE
REFRESH FAST ON COMMIT
AS SELECT * FROM MATVW_A;
MATVW_C
CREATE MATERIALIZED VIEW MATVW_C BUILD IMMEDIATE
REFRESH FAST ON COMMIT
AS SELECT * FROM MATVW_B;
I created a snapshotgroup SNGRP with all the above materialized views.
DBMS_REFRESH.MAKE(name => 'SNGRP',
tab => 'MATVW_A,MATVW_B,MATVW_C',
next_date => TRUNC(sysdate) + 1,
interval => 'SYSDATE + 1');
The order of refreshing the materialized views would be like first materialized view MATVW_A should get refresh then after MATVW_B,MATVW_C.
As they are dependent views.Is there anyway where we can mention the order of refreshing materialized views in snapshot group.
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Mar 25, 2009
Suppose I have materialized view A,B,C. Now I have a new materialized view D which is created from A,B,C. Can I put D into same refresh group?
I am not sure whether D will be refreshed first before A,B,C, resulting that D do not get any update If that is the case, the result will be wrong
If we cannot use refresh group to update nested materialized view, what should we do?
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Jun 19, 2008
CREATE Materialized View log on t1 with rowid;
CREATE Materialized View log on t2 with rowid;
CREATE Materialized View log on t3 with rowid;
CREATE Materialized View MV_test
BUILD IMMEDIATE
FAST REFRESH ON COMMIT
[code].......
I have created a Materialized View by joining the above 3 tables. The Materialized View logs with ROWID has been created on each of the 3 base tables. One of the base tables has around 160 million rows and i expect the Materialized View to have the same number of rows.
The Materialized View has been built for FAST REFRESH on COMMIT. The SELECT list of the CREATE Materialized View statement includes all the ROWIDS from each base tables for doing the fast refresh.
The DBMS_MVIEW explain view shows that the view is capable of doing fast refresh on any DML. The Materialized View took 3 hrs to get built. I have also created indexes on all the three rowid columns (t1rowid,t2rowid,t3rowid) on the Materialized View.
Now, When i do any update on one of the base table and do a commit,
UPDATE t1 set value=500 where tx_id='1234';
The commit is taking around around 15 minutes. I have generated the trace and had a look at it, and it shows that, to refresh the Materialized View, ORACLE is first deleting that record from the Materialized View and then inserting the new record from the base table to the Materialized View.
This delete done by oracle is being done on the basis of the rowid of the updated record stored on the Materialized View log,
However its not using the index created on the t1rowid of the Materialized View and doing a full scan of the MV and hence the delete is taking a lot of time. The delete statement is using a hint NO_MERGE and HASH_SJ which is causing it to do the full table scan of the MV. why is ORACLE not using the index on the t1rowid column of the MV to do this delete?
Also to do the insert in the MV, its selecting the new changed value from the base tables t1,t2 and t2. Here again its doing a full table scan of the base table t1, rather then using the rowid directly or the index coulmn.which is taking a lot of time.
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Aug 20, 2009
CREATE MATERIALIZED VIEW LOG ON ABC;
CREATE MATERIALIZED VIEW MV_ABC
REFRESH FAST
START WITH SYSDATE
NEXT SYSDATE+20/(24*60)
FOR UPDATE
AS
SELECT * FROM ABC WHERE TMSTP> SYSDATE-1;
It is working fine. Appended the Query with WHERE clause in MV_ABC MVIEWS.
DROP MATERIALIZED VIEW LOG ON ABC;
DROP MATERIALIZED VIEW MV_ABC;
CREATE MATERIALIZED VIEW LOG ON ABC;
CREATE MATERIALIZED VIEW MV_ABC
REFRESH FAST
START WITH SYSDATE
NEXT SYSDATE+20/(24*60)
FOR UPDATE
AS
SELECT * FROM ABC WHERE TMSTP> SYSDATE-1;
ORA-12013: updatable materialized VIEWS must be simple enough TO DO fast refresh
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Jan 6, 2010
I am working on materialized view replication but i have an crucial issue. I have a refresh group which contain many MVs some are Read only and some are update but all are in Fast refresh mode (logs are created on both replication and MV sites on these objects) and are referentially integrated to each other i.e they have parent child relationship with each other as at replication site on base tables.
When refresh group job runs to refresh these MVs i got the errors
ORA-02292: integrity constraint (string.string) violated - child record found
After that job status has changed to break,but in the same time all the pending transactions at the MVs sites are pushed to Replication site i e ( Base tables at replication site and MVs of these tables are synchronized).In order to change the status of job to Normal, i have to disable some constraints(not all) on the MVs and manually run the job .After that job status will become Normal even i enable these constraints with validation.
What will be the reason ? Are there some MVs trying to complete refresh instead of Fast or increment refresh in this refresh group?If yes how i can trace out MVs and solve this problem?
Some other information ,
Replication site running with 10gR2 Enterprise Edition.
Materialized View site running with 10gR2 Slandered Edition.
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Jul 7, 2010
I have to convert some existing materialized views (fast refresh) to partition materialized views.
Database version is oracle 10.1.0.4. I have decided to use on prebuilt table option to do the partitioning as it minimizes the time to transfer from the master site.
1) stop replication
1) create interim tables with similar structure as the materialized views
2) transfer all data from the materialized views to the interim tables
4) script out the materialized views structure and add in on prebuilt table option in the scripts
5) drop the materialized views
6) rename the interim tables with the same name as the materialized views
7) run the scripts to create the materialized views with on prebuilt table option
8) refresh the newly created materialized views -> it should take a short time since I am using on prebuilt table option
But I am facing one major issue. That is if I drop the materialized views, the materialized view logs of the master tables are purged. When the materialized views are refreshed fast, there are some data missing. the data that are purged out when the materialized view are dropped.
Do you happen to know other ways that existing materialized views can be converted to partitioned materialized views? Do you have any workaround to prevent the materialized view logs from being purged?
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Aug 4, 2011
I have a created a materialized view which is based on a view on remote database. Now how do I refresh the view.
Materialized view is created by
CREATE MATERIALIZED VIEW mv_employee_name
AS SELECT EMPLID, EMPL_NAME
FROM VEMPDATA@REMOTEDB
WHERE REGION = 'US';
I am wondering how the refersh happens or how do I specify the refresh clause.REFRESH FAST option is looking for VIEW LOG on the master table but in this case its a remote view, so I cannot create any object on remote db.
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Nov 4, 2012
I have 3 reporting tables with 2.2 million records each being rebuilt nightly. The data is used online 24/7 by users and thus, snapshot tables are being built from the refreshed reporting tables. The current method to do this:
delete from snapshot table;
insert into snapshot table (select * from report table);
<repeat for other 2 tables>
commit;
This seems to me to be resource intense on the system even though the table is defined with nologging option.
Is it better to create a MV (select only with refresh complete on demand)? The query is very simple without joins so it at first seems like overkill. However, I am also seeing that dbms_mview.refresh allows for an atomic option. Thus, if 1 of the 3 MVs fails during refresh all 3 rollback, which is a nice feature.
Are there better ways to replicate a snapshot table that I've missed? Is a delete and insert strategy a bad idea?
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Jan 20, 2009
Materialized views are normally used for summarized data access.
CREATE MATERIALIZED VIEW mv_snapshot_A
REFRESH FAST START WITH SYSDATE
NEXT SYSDATE + 20/1440
WITH PRIMARY KEY
AS SELECT * FROM A;
This does not seem to be the case here as the materialized view seems to be just a full select. The overhead of the snapshot logs are concerning for this core table. Can we turn off logging in 10g ? the materialized view is defined as fast refresh/ build immediate .
The main requirement here is to keep the snapshot every 15 minutes so that the users can see the updated information ( the flow of data from one location to other).
User get the location wise count of data and can go further in details like in which location wise system wise data count. As the base table is volatile the materialized view is used so that the moment the user clicks for location wise details the data is static for 15 min and user don't get confused.
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Jul 7, 2008
what is the difference between materialized view and snapshot ?
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Aug 4, 2011
I have a created a materialized view which is based on a view on remote database. Now how do I refresh the view.
Materialized view is created by
CREATE MATERIALIZED VIEW mv_employee_name
AS SELECT EMPLID, EMPL_NAME
FROM VEMPDATA@REMOTEDB
WHERE REGION = 'US';
how the refersh happens or how do I specify the refresh clause.
REFRESH FAST option is looking for VIEW LOG on the master table but in this case its a remote view, so I cannot create any object on remote db.
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Nov 28, 2011
I have n number of materialized views in my schema ..I want to refresh all M_views at once by using cursor
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Sep 11, 2013
I have 5 MViews that I want to refresh in two occasions, every Sundays and at the 1st of the month. I created a Refresh Group for the weekly and that work fine. But when I tried to created the second Refresh Group for the monthly I get a "materialized view is already in a refresh group".
You can only have a materialized view in one refresh group? What options to I have to refresh it in different intervals?
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Sep 29, 2010
We recently migrated a database from 9i to 10g (overdue we know!!) and discovered that dbms_mview.refresh default behavior was turned upside down - meaning that 10g didn't first truncate the MV to refresh it. We're trying to unwind a lot of legacy issues, but it also turns out that we also have 100 REFRESH GROUPs and 100 MATERIALIZED VIEWs. That means a 1 to 1 relationship between RGs vs MVs. There is one MV defined to each RG.
These are my questions:
1) Does a 1 to 1 relationship between RGs and MVs make sense to anybody? The original implementors are gone and we can't fathom the reason for this.
2) Is there any reason why I shouldn't convert these 100 groups to plain and simple 100 MVs? I don't want the delete/insert refresh behavior of dbms_refresh.refresh and I do want the truncate behavior of dbms_mview.refresh ATOMIC=FALSE for refreshing a standard MVIEW
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Dec 10, 2012
I'd like to set up a new Oracle Materialzed View to automatically default to refresh FAST every hour. I have no trouble setting this up in the CREATE MATERIALIZED VIEW statement. However, we will occasionally be performing table maintenance on the table referenced by the MV. At that time I would like to use dbms_mview.REFRESH to execute a refresh ON COMMAND (either F or C depending on the operation weperformed on the table). I have read that this will override the automatic refresh every hour that was set up for the MV when it was created. However - wil the override be permanent? Or will the MV continue to automaticaly FAST refresh every hour after the ON COMMAND refresh is completed?
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Jun 17, 2010
We are planning to create a materialized view on 5 tables and 2 views. After first complete refresh we want to do Fast refresh going forward and planning to create view log for base tables. Since the SQL uses two views, we can create view-log for its underlying tables. But will that work ? In case of fast refresh ? or it will still go for complete refresh ?
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Oct 25, 2011
for following two questions.
1. I have created a materialized view with following syntax in 11g R1 database.
CREATE MATERIALIZED VIEW fr_emp_bonus_record_vw
BUILD IMMEDIATE
REFRESH COMPLETE
START WITH SYSDATE NEXT SYSDATE+1/48
ENABLE QUERY REWRITE AS
SELECT person_id, <columns>
This MV will have around 300K records and this MV will be used in other queries based on person_id. So I have created an index on mv.person_id with following syntax. I have chosen REFRESH COMPLETE, I am assuming that, Oracle truncates this table and recreates it. When it recreates this MV, does it analyze automatically or do I need to do it manually.
CREATE UNIQUE INDEX mv_u1 ON mv(person_id);
2. It takes around 2 minutes to populate 300K. While it is populating the data, if somebody accessing this view or query where this view is being used, are they going to get any error?
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Apr 8, 2012
There is a database db1 which has user U1 in in it contains T1 as table.
Likely,
There is also another database db2 which also has a user named U2 containing table T2 in it.
Now
I want to use the concept of JOINS and Join Table T1 of database named DB1 and Table T2 of database named DB2 and access from database named DB3 using Materialized View Concept.
what shall i do to access tables of DB1 and DB2 from database DB3 using Materialized View.
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Apr 1, 2009
I have a view with complex query that have grouping and aggregations in sub-queries.
Now we would like to change it to a materialized view. However, materialized view does not support GROUP BY clause in sub-query. The solution is to create several view for the sub-queries and then create a materialized view based on it. It seems it can work, but I guest every time complete refresh is required.
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Oct 3, 2009
I have a database link between 2 databases and that works fine. Now the tables of one database are having thier materialized views in the other. The materialized views are not getting refreshed. They hang when i try refreshing them. I have tried everything said on the forums. I changed the job_queue_processes. Also changed the query_reqrite_enabled to true. Still it won't work.
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Jul 15, 2009
Any best way to gather statistics on Materialized Views.
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May 17, 2009
I have a Problem regarding Data Replication, I am using Standard Version of Oracle 9i,I am having 5 remote servers , I am replicating the data from all of these servers using Materialized views on a Centralized server , I have created 5 schema for them, there is a application which is Consolidating the Data from all the locations.
When I create materialized views from these Materialized views I am facing problems to Fast refresh them as I am using "Union All" to combine data of all Users (Error is ora -12004) . I would like to know that is there any other way to do this, also I have tried all the ways to solve the problem of Ora-12004.
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Apr 1, 2009
I have a Materialized view based on 2 views. I modified one column in both the views.Do i need to refresh the Materialized view.
E.g. :
In view1 and view2 i changed column like this
nvl(test.no,'n/a') testdata --changed
nvl(test.id,'n/a') testdata --original
CREATE MATERIALIZED VIEW MV_test
NOCACHE
LOGGING
NOCOMPRESS
NOPARALLEL
BUILD IMMEDIATE
[code].........
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Sep 12, 2008
I have attempted to set up the materialized view below to refresh complete at the time specified below. The problem is that it does not refresh and pick up the changes to one of the base tables.
When I issue the command:
exec DBMS_REFRESH.REFRESH('TEAMSITE3.FIRMSEARCH_COWS_MV ');
the refresh works..
why this view is not refreshing at the time stated??
CREATE MATERIALIZED VIEW FIRMSEARCH_COWS_MV
REFRESH COMPLETE START WITH to_date('11-09-2008 10:00:00','dd-MM-yyyy hh24:mi:ss') NEXT (SYSDATE+1)
AS SELECT distinct spar.COW_REF
FROM LV_RECOGNISED_ATTAINMENTS lra,
LV_POSITION_IN_ORGANISATIONS rio,
[code]....
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Nov 22, 2007
Have some issue with Materialized view refresh. Have presented scenario which we have .
Schema1 :
1. Have base tables
2. Created MV logs on base tables
Schema2 :
1. Created sysnonyms for Schema1 base tables
2. created Materialized views
3. Created MV group , added views to the group
Executing the below command in schema2 :
execute dbms_refresh.refresh('MV_grp');
Error :
ORA-12048: error encountered while refreshing materialized view
"Schema2"."Table1_MV"
ORA-12018: following error encountered during code generation for
"Schema2"."Table1_MV
"ORA-00942: table or view does not exist
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 2255
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 2461
ORA-06512: at "SYS.DBMS_IREFRESH", line 683
ORA-06512: at "SYS.DBMS_REFRESH", line 195
ORA-06512: at line 1
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Mar 4, 2011
while replicating the master site via materialized views, in mViewGroups i issued:
BEGIN
DBMS_REFRESH.MAKE (
name => 'mvadmin.hamza_refg',
list => '',
next_date => SYSDATE,
interval => 'SYSDATE + 1/1440', -- for test purpose i used such a small interval
implicit_destroy => FALSE,
rollback_seg => '',
push_deferred_rpc => TRUE,
refresh_after_errors => FALSE);
END;
in my previous attempt it worked all fine... i had a change in senerio, so i did my replication again from scractch using the same old spool in a new installation but even after 3 tries on replicating from scratch my objects are not getting refreshed automatically. even when i attempt to refresh the group it does not work. it works only when i refresh each of the participating object of the group manually.
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Nov 11, 2008
I have a table in one database and I want to replicate it in another two databases with materialized views. The refresh may be fast. Is this possible?
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Oct 15, 2011
We have some materialized views in our environment which refreshes after every 1 hour. In the same environment, we have some big processes and we do not want the performance of these big processes to get affected because of refreshing these materialized views.
if there is a way to pause the refreshing of materialized views before running the big processes and later after the big processes are completed, then resume the refreshing of the materialized views?
One way I can think of is to drop the materialized views and create the materialized views back.
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Jul 28, 2008
I have one question on MVIEWS.....
Where the logs will be logged for all the materialized views transactions (I mean a particular table)?
Is there any Data Dictionary Table were i can find this .
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Jul 25, 2008
How to reset the status of Refresh Group?
In our database, it is showing the status of Refresh group to 'Broken'.
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