Performance consequences to adding materialized view logs to tables?

I am writing a very complex query for a client of our transactional database system and this will require the creation of a materialized viewbecause all attempts at tuning to make performance acceptable have failed.
I want to enable fast refresh of the MVIEW but I am confused regarding the consequences of the addition of adding materialized view logs to the base tables.
Some of the tables are large and involved in alot of transactions and I am wondering if the performance of INSERT/UPDATES will be seriously affected by the presence of an mview log.
This may be a simple question to answer but I was unable to find a clear cut answer in the literature.
Thanks for any answers!!
Chris Mills
Biotechnology Data Management Consultant

Last time i looked into this there were three cases to consider
If you're doing conventional row-by-row DML then the impact is just one insert into a heap table per row modified.
If you are modifying a high number of rows using bulk-binds then the overhead is very severe because modifying 1,000 rows on the base table causes 1,000 non-bulk bound inserts into the log table.
Direct path inserts have extremely low overhead because the MV log is not touched. Instead, the range of new rowids added is logged in ALL_SUMDELTA
http://oraclesponge.wordpress.com/2005/09/15/optimizing-materialized-views-part-ii-the-direct-path-insert-enhancement/

Similar Messages

ORA-12034: materialized view log on table younger than last refresh

I am getting this error while creating the materialized view.
This error seems to be refresh error.
but when i have a mat view log already and running script to create the materialized view how can that happen?

34MCA2K2, Google lover?
I confess perhaps I gave a little info.
View log was created before MV.
It was the first initial load.
No refresh failed.
No DDL.
No purge log.
Not warehouse.
There is no such behavior for MVs on another sites.
P.S. I ask help someone who knows what's wrong or who faced with it or can me follow by usefull link.
P.P.S. It's a pity that there is no button "Useless answer"

Can't update master table when creating a materialized view log.

Hi all,
I am facing a very strange issue when trying to update a table on which I have created a materialized view log (to enable downstream fast refresh of MV's). The database I am working on is 10.2.0.4. Here is my issue:
1. I can successfully update (via merge) a dimension table, call it TABLEA, with 100k updates. However when I create a materialized view log on TABLEA the merge statement hangs (I killed the query after leaving it to run for 8 hrs!). TABLEA has 11m records and has a number of indexes (bitmaps and btree) and constraints on it.
2. I then create a copy of TABLEA, call it TABLEB and re-created all the indexes and constraints that exist on TABLEA. I created a materialzied view log on TABLEB and ran the same update....the merge completed in under 5min!
The only difference between TABLEA and TABLEB is that the dimension TABLEA is referenced by a number of FACT tables (by FKs on the FACTS) however this surely should not cause a problem. I don't understand why the merge on TABLEA is not completing...even though it works fine on its copy TABLEB? I have tried rebuilding the indexes on TABLEA but this did not work.
Any help or ideas on this would be most appreciated.
Kind Regards
Mitesh
email: [email protected]

Thats what I thought, the MVL will only read data that has changed since it was created and wont have the option to load in all the data as though it was made before the table was created.
From what I have read, the MVL is quicker than a Trigger and I have some free code that prooved to work from a MVL using it as a reference to know what records to update. There is not that much to a MVL, a record ID and type of update, New, Update or Delete.
I think what I will have to do is work on a the same principle for the MVL but use a Trigger as this way we can do a full reload if required at any point.
Many thanks for your help.

ORA-12096: error in materialized view log

Hi All,
I had created a fast refresh materialized view. Log was also created.
Now i dropped the mv and the logs.
But now every time i update or insert into this customer table i get error message.
ORA-12096: error in materialized view log on Customer
ORA-00942: table or view does not exist
There are entries in the DBA_MVIEW_LOGS for customer table.
Please suggest.

Hi,
What database version are you on?
And do you have access to Metalink/My Oracle Support?
Found this, by the way:
ORA-12096: error in materialized view log on <table>
If problems occur when you try to access a log file for a materialized view, the system issues an ORA-12096 error message which is followed by the actual error. If the ORA-12096 error message is accompanied by an ORA-00942 message, the problem may be due to an online reorganization that was only partially undone. In this case, you can drop the log file for the materialized view manually (after you have verified that it is no longer required):
DROP MATERIALIZED VIEW LOG ON <table>;
Edited by: hoek on Jul 29, 2009 2:15 PM

Will Materialized view log reduces the performance of DML statements on the master table

Hi all,
I need to refresh a on demand fast refresh Materialized view in Oracle 11GR2. For this purpose I created a Materialized view log on the table (Non partitioned) in which records will be inserted @ rate of 5000/day as follows.
CREATE MATERIALIZED VIEW LOG ON NOTES NOLOGGING WITH PRIMARY KEY INCLUDING NEW VALUES;
This table already has 20L records and adding this Mview log will reduce the DML performance on the table ?
Please guide me on this.

Having the base table maintain a materialised view log will have an impact on the speed of DML statements - they are doing extra work, which will take extra time. A more sensible question would be to ask whether it will have a significant impact, to which the answer is almost certainly "no".
5000 records inserted a day is nothing. Adding a view log to the heap really shouldn't cause any trouble at all - but ultimately only your own testing can establish that.

Materialized View Logs on OLTP DB- Performance issues

Hi All,
We have a request to check what would be the performance impact of having Matirialized View (with FAST refresh each 5 and each 30 min).
We have been using some APIs( I don't have full details of this job) to refresh tables in Reportign DB and want to switch to MVIEWS in the next release.
The base tables for this MVs are in DB1 with high DML activity.
We are planing to create 7 MVs on a reporting DB pointing to the corresponding tables in DB1.
I am setting up the env with the required tables to test this and also want to know your experiences in implementing Mviews with Fast refresh pointing to a typical OLTP DB as I am new to MVIEWS.
How it affects the performance of DML statements on base tables?
How often you had to do complete refresh because of invalid/outdated Mview Logs?
other Maintenance overheads?
any possible workarounds?
Oracle Version: 9.2.0.8
OS : HP-UX
Thank you for sharing your experiences.

Doing incremental refreshes every 5 minutes willadd some amount of load to the OLTP system. Again,
depending on your environment, that may or may not be
significant.
what factors can effet this? Among other things, the size of the materialized view logs that need to be read, which in turn depends on the number of transactions and the setup of the materialized views, the current load on the OLTP system, etc. If you're struggling with an I/O or CPU bottleneck at peak processing now, for example, having a dozen materialized view refresh processes running as well would probably generate noticable delays in the system. If you have plenty of spare CPU & I/O bandwidth, the refreshes will be less noticable.
is it the same in 10g R2 too? we are upgrading to the
same in coming October.Streams is far easier to deal with in 10.2.
Justin

Creation of Materialized view and Materialized view log.

I wanted to create materialized view with 'REFRESH FAST ON COMMIT' option.
1) Table1 --it is partitioned range + list -- Added primary key
2) view1   -- having primary keys on view's base table
Steps:
1) create materialized view log on Table1 ; -- default primary key
2) create materialized view log on view1. --- It is giving below error.
ORA-00942: table or view does not exist
i wanted to create Materialized view like below
create materialized view
REFRESH fast ON commit
as
select ...
... from table1
where c1 in (select c1 from view1 where ... );
Question:
1) As i am getting above error while creating MV log on view. Can we create MV log on view or we have to create MV log on view base table?
2) To create MV with ''REFRESH FAST ON COMMIT' option , do we need to have primary key on master tables?
Any pointers on this will really helpful.
Thanks
Prasad

Also created MV LOG on 3 tables and tried with joins ..
create materialized view
REFRESH fast ON commit
as
select ...
... from table1 , tab2 t2,tab3 t3
where ....
and ...
Get same error ORA-12052: cannot fast refresh materialized view AVSYS.EVENT_LOG_MV
2052. 00000 - "cannot fast refresh materialized view %s.%s"
*Cause:    Either ROWIDs of certain tables were missing in the definition or
           the inner table of an outer join did not have UNIQUE constraints on
           join columns.
*Action:   Specify the FORCE or COMPLETE option. If this error is got
           during creation, the materialized view definition may have be
           changed. Refer to the documentation on materialized views.

Query on Materialized view and materialized view log

I am creating a materialized view something like this.but getting following error:
ERROR at line 1:
ORA-12032: cannot use rowid column from materialized view log on "SCOTT"."EMP"
SQL> create snapshot log on scott.emp;
Materialized view log created.
SQL> create materialized view scott_emp refresh fast on demand as select deptno,sum(sal) sum_sal from scott.emp group by deptno;
ERROR at line 1:
ORA-12032: cannot use rowid column from materialized view log on "SCOTT"."EMP"
Note when i have my query in materialized view as "select * from emp;" in place of
"select deptno,sum(sal) sum_sal from scott.emp group by deptno;" This code works fine.
How do i have a materialized with with a group by clause.
Thanks in Advance

Got the answer myself.
I wasnt adding all the required columns.
CREATE MATERIALIZED VIEW LOG ON scott.emp
WITH SEQUENCE, ROWID (<all the required columns>)
INCLUDING NEW VALUES;
Anyways,
Thanks guys...

Truncate table and materialized view log

I user oracle 10 R2
I have a table and on that table a materialized view log.
I execute in a pl/sql procedure:
1) execute immediate('drop materialized view log on tab1');
then:
2) execute immediate('truncate table tab1');
3) Now I insert a lot of records in tab1
4) execute immediate('create materialized view log on tab1 WITH rowid INCLUDING NEW VALUES');
When I create the materialized view log I recieved this message:
ora32321: refresh fast on tab2 unsupported after detail table truncate
Why?

Refresh fast after truncate operation on container table is not supported, regardless the container table is or is not partitioned.
Perform a refresh complete.
ORA-32321 :
Cause:     A detail table has been truncated and no materialized view
     supports fast refersh after a detail table has been truncated
Action:     Use REFRESH COMPLETE. Note: you can determine why your
     materialized view does not support fast refresh after TRUNCATE
     using the DBMS_MVIEW.EXPLAIN_MV() API.

Disabling Materialized View Logs for a session

Hi all.
I was wondering if it is possible to disable the fast refresh log for materialized views for just a given session. So for all other sessions except this one the log would be added to. I'm using 11g.
In Oracle Database 11g, The Complete Reference on page 447 it states:
"As of Oracle 11g, the capture of changes in materialized view logs can be disabled for an individual session while logging continues for changes made by other sessions". But no instructions are given
Does anyone know how to do this? I have not been able to find the answer by looking around.
Thanks!

Yeah, I had saw that Oracle mentioned it here also: http://download.oracle.com/docs/cd/B28359_01/server.111/b28279/chapter1.htm#FEATURENO07197
Any idea of what the code might look like? I've never had to alter an individual session for Oracle before.

Materialized view log timestamp

I'm arranging materialized view logs for my developers that need to collect just the delta of some tables.
I've created materialized view logs with option sequence so that they can have an additional ordering information.
They are now asking me if there is an option for collecting even the transaction timestamp.
I didn't find any thing better solution then adding a trigger on each mview log which writes sequence and timestamp on separate table.
I don't want to use this additional triggers. Is there an option/workaround on mview logs to gather even this transaction timestamp?
thanks in advance for your response,
Max

Ask your developers to add the TIMESTAMP column and trigger.

Materialized View Log not empty

Hello all
I have an oracle database (11g version), connecting via dbLink to another DB (10g version), and using it's tables as masters for fast refresh materialized views.
To make it simple: I have master DB, with master table X, and Materialized View Log MLOG$_X.
Then, I have replicate DB, with dblink pointing to Master, and Materialized View MV_X, using X.
The materialized view is refreshed fast, on demand.
The problem is, the MV log is never getting empty... how can I solve this issue?
/* code for creating MView */
CREATE MATERIALIZED VIEW "MY_USER"."SI_BANK" ("ID", "NAME", "ACRONYM")
ORGANIZATION HEAP PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING
STORAGE(INITIAL 163840 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "USERS"
BUILD IMMEDIATE
USING INDEX
REFRESH FAST ON DEMAND START WITH sysdate+0 NEXT SYSDATE + 1
WITH PRIMARY KEY USING DEFAULT LOCAL ROLLBACK SEGMENT
USING ENFORCED CONSTRAINTS DISABLE QUERY REWRITE
AS SELECT ibanco id, nbanco name, nsigla acronym FROM USER.tgtbanc0@DB_LINK;
/* code for refresh group*/
BEGIN
DBMS_REFRESH.MAKE ( name => 'si2p_grp',
list => '', next_date => 'SYSDATE +1' , interval => 'SYSDATE + 1', implicit_destroy => FALSE, rollback_seg => '', push_deferred_rpc => TRUE, refresh_after_errors => FALSE);
END;
/* ADD MATERIALIZED VIEWS TO GROUP */
BEGIN
DBMS_REFRESH.ADD ( name => 'si2p_grp', list => 'SI_BANK', lax => TRUE);
END;
Thank you for any help

One MV log serve to many materialized views. Check dba_registered_mviews on master DB to see how many MViews you have build on you master table X.
After MV (materialized view) is refreshed than all data logged in MVlog for this MV are deleted. But new are recorded when DML are performed against table X.
If you can stop DML on table X for some period of time then do MV refresh and then you can see that MVlog is empty.

Creating a Materialized View Log After the Data has been instered

Hi,
I am trying to create a method of replication from Oracle to MySQL using the Materialized View Log table.
This has been done before and works quite well, the only problem is that I am trying to impliment the log after the table has been created and populated and wish to push all the existing data through the log file...
Does anyone know if it is possible to refresh the Materialized View Log and not a Materialized View.
The way the replication is intended to work is:
Oracle> Data inserted into table
Oracle> writes the vector data to the MVL
Script> Monitors the MVL and can see the changes being made to the Oracle Table
Script> Updates MySQL with the data and removes the rows from the MVL
MySQL is then used with other unix systems
Currently we export the data from the table using Triggers and a cronjob running every x minute to check for changes in the TriggerTables
Many thanks for your time on this, I have been checking for almost a whole working day and not found the answer to this problem.

Thats what I thought, the MVL will only read data that has changed since it was created and wont have the option to load in all the data as though it was made before the table was created.
From what I have read, the MVL is quicker than a Trigger and I have some free code that prooved to work from a MVL using it as a reference to know what records to update. There is not that much to a MVL, a record ID and type of update, New, Update or Delete.
I think what I will have to do is work on a the same principle for the MVL but use a Trigger as this way we can do a full reload if required at any point.
Many thanks for your help.

Materialized view (fast refresh mode) + Materialized view log on another DB

Hi all,
I created a materizalied view using this script :
CREATE MATERIALIZED VIEW GIPS.DOSSIER_MEDICAL_MV2
TABLESPACE GIPS_T
NOCACHE
NOLOGGING
NOCOMPRESS
NOPARALLEL
BUILD IMMEDIATE
USING INDEX
TABLESPACE GIPS_I
+ REFRESH FAST ON DEMAND +
START WITH TO_DATE('11-janv.-2011 16:00:00','dd-mon-yyyy hh24:mi:ss')
NEXT sysdate (1/96)+
AS
SELECT N0_SEQ_BLOB_PDF,
EXAM_ID,
MPR,
RSM,
rub,
date_deb,
SPE,
commentaire,
SPR,
MEP,
MSJ,
TTD,
exam_type
FROM DOSSIER_MEDICAL@dbdoc_lk
WHERE DOSSIER_MEDICAL.EXAM_TYPE IN ('TELEM', 'SCANNER', 'EPPO_SECMED');
So you can see I'm using a dblink in the select statement ( DBDOC_LK )
On the DB referenced by this dblink, I created a materialized view log using this script :
CREATE MATERIALIZED VIEW LOG ON "DOSMED"."DOSSIER_MEDICAL"
TABLESPACE "DOC_T"
WITH PRIMARY KEY
INCLUDING NEW VALUES;
The problem is that my materialized view has never refreshed since its creation ! and I don't understand why ?
Can someone help me ?
Thank you.

The REFRESH schedule causes a job to be created for the execution of the Refresh. You should see this job in DBA_JOBS / USER_JOBS.
The job would run only if the instance parameter JOB_QUEUE_PROCESSES is set to 1 or higher (the default is 0). This parameter can be modified dynamically with an ALTER SYSTEM command.
Hemant K Chitale
http://hemantoracledba.blogspot.com

How to CREATE MATERIALIZED VIEW LOG (MV fast refresh) with some JOINS

Hi @ all,
i'm trying to create a MATERIALIZED VIEW LOG for a fast refresh of a MATERIALIZED VIEW.
It works fine with a simple Request in the MATERIALIZED VIEW:
CREATE MATERIALIZED VIEW MV_ZOTD43_P
TABLESPACE GDII
BUILD IMMEDIATE
REFRESH FORCE AS
SELECT * FROM ZOTD43_P;
COMMIT;
CREATE MATERIALIZED VIEW LOG ON ZOTD43_P
TABLESPACE "GDII"
WITH PRIMARY KEY, ROWID, SEQUENCE INCLUDING NEW VALUES;
call DBMS_MVIEW.REFRESH('MV_ZOTD43_P', 'f');
But when I use a complex SQL-Request with some JOINS (one of the Table with spatial Data) in the MATERIALIZED VIEW, I get an error:
CREATE MATERIALIZED VIEW MV_TEST
TABLESPACE GDII
BUILD IMMEDIATE
REFRESH FORCE AS
SELECT lptd04_p.sst_nr AS sst_nr,
lptd03_p.aaaa AS aaaa,
lptd04_geom.geom as geom
FROM lptd04_p lptd04_p
JOIN lptd01_p lptd01_p ON lptd01_p.cre_nr = lptd04_p.sst_nr
JOIN lptd04_geom ON lptd04_geom.sst_nr = lptd04_p.sst_nr
JOIN lptd03_p lptd03_p ON lptd03_p.lief_nr = lptd04_p.lief_nr;
COMMIT;
CREATE MATERIALIZED VIEW LOG ON LPTD04_P
TABLESPACE "GDII"
WITH PRIMARY KEY, ROWID, SEQUENCE INCLUDING NEW VALUES;
call DBMS_MVIEW.REFRESH('MV_TEST', 'f');
Error report:
SQL Error: ORA-12004: REFRESH FAST kann für Materialized View "GDI"."MV_GDI_SST_STAMM" nicht benutzt werden
ORA-06512: in "SYS.DBMS_SNAPSHOT", Zeile 2255
ORA-06512: in "SYS.DBMS_SNAPSHOT", Zeile 2461
ORA-06512: in "SYS.DBMS_SNAPSHOT", Zeile 2430
ORA-06512: in Zeile 1
12004. 00000 - "REFRESH FAST cannot be used for materialized view \"%s\".\"%s\""
*Cause: The materialized view log does not exist or cannot be used. PCT
refresh is also not enabled on the materialized view
*Action: Use just REFRESH, which will reinstantiate the entire table.
If a materialized view log exists and the form of the materialized
view allows the use of a materialized view log or PCT refresh is
possible after a given set of changes, REFRESH FAST will
be available starting the next time the materialized view is
refreshed.
Am I doing something wrong or is it not possible CREATE MATERIALIZED VIEW LOG when the MATERIALIZED VIEW got some JOINS?
Regards,
Greq

Thanks for the link Alessandro ,
the error seems something to do with the Column-Type SDO_GEOMETRY, so
i create a new thread in the Spatial Discussion forum:
FAST REFRESHing of Oracle Materialized Views containing SDO_GEOMETRY column
Regards,
Greq

Performance consequences to adding materialized view logs to tables?

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