Replication :: Materialized View Fast Refreshes Are Slow?
Jun 28, 2009
I created a Materialized view using joining of two tables with FAST REFRESH ON COMMIT option. These tables are the main tables of the DB and contains alot of data(about 15 millions of records). two master tables have index but mview doesn't have any indexes. I've thought the entire concept of the fast refresh is that it should be a relatively quick operation but the result showed that DB performance reduced, for example I could insert 900 records per minute thru application into master tables before but now I can just insert about 400 records per hour!.Also, It slows down the select operation, went from 0.11 seconds(with joining two tables) to 33 seconds (in mview)!.
First of all, I considered following possibilities and test them:
1) The most likely solution was that a complete refresh was happening. However, the materialized view refresh was confirmed to be a fast refresh by querying USER_MVIEWS.
2) I checked the query of the materialized view and confirmed that it was a simple select from the master tables without any aggregation or sorting.
3) DBMS_MVIEW.explain_mview was run on the materialized view. MV_CAPABILITIES_TABLE did not reveal any problems.
4) A query of dba_registered_snapshots showed that no other snapshots appeared to be using these logs. So, After each refresh, the records in mview logs were deleting.
As you see, it seems everything is ok, but what was causing this fast refresh to go so slow?
I use oracle 10.2 on Suse Linux enterprise server.
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Nov 1, 2012
The customer moved their database from 10g to a 11gR2 database.They created the MV in the new system and now it takes 26 hours to refresh as opposed to 15 min in the old 10g database.Just looking for a game plan for troubleshooting.
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Jan 4, 2008
I am having two server A and B.B is the replica of A.I have to alter the materialized view of one of the table in server B,of which Master table is in both the servers .I do not have any Materialized view log on both the servers and want to convert the Refresh method from Complete to Fast refresh.One way of this altration is to create materialized view log on master table.
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Sep 4, 2008
We are facing serious problem while refreshing materialized views using fast refresh option in ORACLE..For the very first time we are performing Complete refresh of data from DB1 to DB2 for few tables.Ongoing we are performing Fast Refresh.Sometimes the fast refresh works fine without any error and sometimes it fails with the below error.
ERROR at line 1:
ORA-32320: REFRESH FAST of "CIR"."C_BO_COMM" unsupported after
cointainer table
PMOPs
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 803
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 860
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 841
ORA-06512: at line 1
let me know when will this error occur during Fast Refresh.
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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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Jun 20, 2011
i have created a fast refresh materialized view but it is not performing fast refresh or even complete refresh.Then i have checked my materialized view capabilities then in mv_capabilities_table i got a message that materialized view log is newer than old .
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Feb 8, 2012
I'm trying to build up a materialized view with aggregate and FAST REFRESH for INSERT and UPDATE, DELETE with no success. But the web doesn't deny it ?
--build up needed schema objects
CREATE TABLE empt
( ename VARCHAR2(20),
empno INTEGER,
[Code]....
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Oct 10, 2013
I've 2 tables in schema A.
1) TXN_HD_FCT (This table has 6 billion records. Has fields TXN_DT, CUST_ID, TXN_AMT, TXN_ID and the table is partitioned on TXN_DT. We load data approximately 600K+ records to this table every day
2) RELINK_CUST (This table has 2 fieds CUST_ID and NEW_CUST_ID). We load data approximatley 100-200K+ records every day into this table. This table has total 10MM+ records now.
Now i need to create a table (TXN_UPD_HDR_FCT) in Schema B by joining above 2 tables using below query every day
CREATE TABLE TXN_UPD_HDR_FCT
select a.TXN_DT,
nvl(b.new_cust_id, a.cust_id) as cust_id,
a.txn_amt,
a.txn_id,
from schema_A.TXN_HD_FCT a,
schema_A.RELINK_CUST b
where a.cust_id = b.cust_id(+);
We update CUST_ID to NEW_CUST_ID based on some rules (and keep it in the table RELINK_CUST) and need to take this new_cust_id while building the table TXN_UPD_HDR_FCT.
Building this table is taking approximately 4+ hours every day. just refresh only records from TXN_HDR_FCT whose CUST_ID is changed or any records inserted into TXN_HDR_FCT? I read about Materialized views but not sure how can i create MV logs on 2 tables? If i use materialized views do i need to create indexes every day?
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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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Mar 6, 2013
I have a view that includes sub queries in its select.
I am creating a MV over that view. and i want to fast refresh it when ever a commit is placed on the table (that is used in the from clause for the simple view)
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Sep 26, 2013
create materialized view ino_crm.MV_IDENTIFICATION_DETAILS REFRESH FAST as SELECT billing_account_id, i.s1 KEYS_ , COALESCE(i.s2, i.b, i.d) VALUES_ FROM ba_personal_details pd , xmltable ( '//entry[string = "identification Details"]//entry' passing xmltype(pd.details) columns s1 VARCHAR2 (255) path 'string[1]' ,s2 VARCHAR2(255) path 'string[2]' ,b VARCHAR2(255) path 'boolean' ,d VARCHAR2(255) path 'date' ) i WHERE pd.mandator_key = 'VSO01' AND pd.valid_to = to_date('01.01.4000', 'DD.MM.YYYY'); and
I get an exception like: SQL Error: ORA-12015: cannot create a fast refresh materialized view from a complex query 12015. 00000 - "cannot create a fast refresh materialized view from a complex query"
*Cause: Neither ROWIDs and nor primary key constraints are supported for complex queries.
*Action: Reissue the command with the REFRESH FORCE or REFRESH COMPLETE option or create a simple materialized view.
I have found this URL....
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Sep 4, 2009
i need to set up a central server with all the master tables and two other local database which will hold the updatable materialized view of the master table...the databases must be synchronized with central server..and user will work on the materialized view database...
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Jan 16, 2012
I have a base table with ~20 mio. records with two FAST REFRESH Materialized Views based on that table using various aggregate functions in their view definition.
The problem is, when e.g. one record changes in the base table, I see two records in the MV log table MLOG$, but invoking the fast refresh mechanism by using using:
dbms_snapshot.refresh('mv1', 'f');
dbms_snapshot.refresh('mv2', 'f');
Is still running after ~20 minutes now.
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Apr 27, 2011
I'm trying to create materialized view, successfully create logs for all the tables involved.
CREATE MATERIALIZED VIEW LOG ON tbJournal
WITH ROWID, SEQUENCE (tabid, companyid, storelocid, tabstatus, linetype)
INCLUDING NEW VALUES;
CREATE MATERIALIZED VIEW LOG ON TBTABS
WITH ROWID, SEQUENCE (TSTAMP, COMPANYID, NUMGUESTS, POSITIONID, STORELOCID, TABSSTATUS)
INCLUDING NEW VALUES;
[code]....
The result is ora-12015: cannot create a fast refresh materialized view from a complex query
It does work fine if I remove
AND EXISTS (SELECT 1 FROM tbJournal J
WHERE j.tabstatus NOT BETWEEN -6 AND -4
AND j.linetype = 1
AND T.tabid = J.tabid
AND T.companyid = J.companyid
AND T.storelocid = J.storelocid)
from the where clause
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Apr 15, 2010
I have created a MV joining 10 tables with FAST REFRESH ON COMMIT It made my sytem very slow.
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Jan 6, 2013
I had to drop the MV with preserve table and rebuilt it after modifcation of materalized table.Before dropping the materialized view metdata was.
CREATE MATERIALIZED VIEW "DM_TGT_SHARED"."EA_MERGED_DATA_MV"
ORGANIZATION HEAP PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING
STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT)
TABLESPACE "DM_TGT_SHARED"
BUILD IMMEDIATE
USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255
[code]...
now this view taking an ages to refresh as before , there is a MV log i suspect i did not use "with rowid" clause when rebuilding the materliazed view , how can i add with rowid clause which i reckon will improve the MV refreshment.
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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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Jan 9, 2008
I have created materiaized view
Create Materialized View table_name
Tablespace FG_Report
Build Immediate Refresh Force
Start with SYSDATE next SYSDATE+5/1440
As Select * from table_name@dblink;
after creating, i don't see indexes on the the materialized view created. where as in actual table we have indexes..
Can we replicate indexes along with Materialized views?
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May 18, 2009
I have a Materialized View that gets refreshed everyday.While the DB running on oracle 9.2.0.7,It was taking around 50mins to refresh.I was using the following codes
dbms_mview.refresh('mvname','c');
After 10g upgradation the refresh process ran for more than 2 hr.So I used the following codes
dbms_mview.refresh('mvname','atomic_refresh=>false')
It took 50mins to refresh. But what I found that the number of record count is same after each day refresh.Is there any problem with the option atomic_ refresh=>false.Why I used it -In Oracle 9.2.7.0 the 'c' option truncate the MVIEW then insert.But in Oracle 10.2.0.4.0 the 'c' option deletes the records and then insert .The option atomic_refresh=>false truncates.
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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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May 14, 2009
how much would be overhead of materialized view logs against DML on tables with few millions of records?
I need to convince my team lead before moving ahead with materialized view for few reports about overhead so is there any documentation by oracle on this issue?
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Jan 25, 2011
I am confused to see one materialized view is not refreshing automatically, whereas the same thing I can do manually.
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Dec 22, 2005
How can i use refresh option as 1 hr in creation of materialized view, Can i use unoin all in the materialized view and other clause like CONNECT BY PRIOR .
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Jun 16, 2008
We are using Oracle 10g rel 2. The replication is setup on 1 server which is in City A, and the snapshot server is in City B.
City A .
Create materialized view log on table-a
with primary key
including new values.
City B database.
Create user test_rep identified by test
grant connect, resource, create any materialized view , table, view , procedure to test_rep.
Create materialized view city-A_db_MV
refresh fast
select * from cityA.Tablea@city-Adb
When i select from city-A_db_MV, it showed the complete table-A of city-A database.
Now if we make any changes to City-A table at the Master site, will it be propagated automatically to the MV site.
I guess we need to create jobs to push / or refresh fast .. isnt it. But exactly how to do it is a question.
Secondly if we make a replication group at Master site at city-A db, how do we refresh that Group and how to monitor whether it is refreshing on time or not? do we need to see the jobs every now and then.
but still a lot of questions unanswered, even though i had read the documents earlier.
1-The MView was created without identifying that after what interval it will be fast refreshed.
2- How to Manually refresh it. Does it support On Commit, I think it is not.
3- Where should be we make a group and then add the table to that group and refresh that group.
Should this group belongs to the Master Site or to MV site?
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Mar 13, 2008
I have to create a materialized view for a table which does not have index on any field.
While creating a Mview i am getting an error "TABLE DOES NOT HAVE THE PRIMARY KEY CONSTRAINT".
application developers do not want to create an index on the base table onto which MView is to be created.
is there any way to create a materialised view for the table without index, or is it necessary to have the index on the base table before creating MView on it.
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Nov 5, 2008
How I can create a Materialized View without having any data in it.
For e.g.
I create a Materialialized View based on a View.
CREATE MATERIALIZED VIEW test_mv
REFRESH FORCE ON DEMAND
AS
SELECT * FROM test_view
In the above case the data fetched by the view test_view gets stored in the Materialized View test_mv. Suppose I want materialized view test_mv to get created with all the columns of test_view but not the data. I will refresh the materialized view test_mv later for data as and when required.
What shall I do for immidiate formation of materialized view test_mv without data.
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Jul 7, 2008
what is the difference between materialized view and snapshot ?
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Apr 5, 2012
We have the task to create to Materialized view from oracle 10g to 8i. - Will we face any kind of issue after creation of Materialized view. check what the prerequisite need to be verified is.
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Sep 5, 2013
I inherited an existing database. I have a materialised view on a table that uses a materialised view log. I have been asked to see if it is possible to categorise the rows by change type (inserted, updated or deleted) and populate another materialised view or table accordingly. If this is possible then how can it be achieved.
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