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How often you had to do complete refresh because of invalid/outdated Mview Logs?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

Similar Messages

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 issue

We are having issues with the size of materialized view logs in one od the database. The size of the log table is around 32G. Will appreciate if somebody will help in explaining why it is having such a huge size and is not getting purged.
At the same time the master table is having comparatively smaller size of 18G(did not check table fragmentation).
Also, please help me in understanding what is required to be done for fixing this issue.
SQL> select LOG_OWNER,MASTER,LOG_TABLE,LOG_TRIGGER,PRIMARY_KEY from dba_mview_logs where log_owner='MARTDATA' and MASTER='POLICY_CONFIGURATION';
LOG_OWNER MASTER LOG_TABLE LOG_TRIGGER PRI
MARTDATA POLICY_CONFIGURATION MLOG$_POLICY_CONFIGURATION NO
SQL> select owner, segment_name, sum(bytes)/1024/1024 "SIZE in MB" from dba_segments where segment_name='POLICY_CONFIGURATION' and owner ='MARTDATA' group by owner, segment_name;
OWNER SEGMENT_NAME SIZE in MB
MARTDATA POLICY_CONFIGURATION 18458
SQL> select owner, segment_name, sum(bytes)/1024/1024 "SIZE in MB" from dba_segments where segment_name='MLOG$_POLICY_CONFIGURATION' and owner ='MARTDATA' group by owner, segment_name;
OWNER SEGMENT_NAME SIZE in MB
MARTDATA MLOG$_POLICY_CONFIGURATION 32298
Thanks

Oracle automatically purges rows in the materialized view log when they are no longer needed. Because Oracle must wait for all dependent materialized views to refresh before purging rows from a materialized view log, unwanted situations can occur that cause a materialized view log to grow indefinitely when multiple materialized views are based on the same master table or master materialized view.
For example, such situations can occur when more than one materialized view is based on a master table or master materialized view and one of the following conditions is true:
Materialized view is not configured for automatic refreshes and has not been manually refreshed for a long time. OR
Materialized view has an infrequent refresh interval, such as every year, etc
You can also refresh the materialized views associated with the log so that Oracle can purge rows from the materialized view log.
If a materialized view log needs to be purged manually for some reason a procedure called DBMS_MVEW.PURGE_LOG can be used.
Edited by: user130038 on Sep 30, 2011 6:49 AM

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/

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.

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

ORA-12096: error in materialized view log on ORA-01301:insufficient privile

Hi,
One of our ebusiness Apps 11510 instances has database that was
upgraded from 9.2.0.6 to 10.2.0.4 with Database Vault.
After that, we are getting an error:
ORA-12096: error in materialized view log on "SCHEMA"."TABLE_NAME" ORA-01301:insufficient privileges
Can you please let know what can be the reason. Which user is being checked for the privileges?
Regards

I am facing the same issue in one of our internal instances.
Apps Environment has been upgraded from Database 9.2.0.6 to Database 10.2.0.4 with Database Vault. We started facing this issue and the same error after the upgrade. MLOG definition has not changed.
What privilege is it expecting to be present for the schema.
The definition of the MLOG is as given below
LOG_TRIGGER = NULL
ROWIDS = YES
PRIMARY_KEY = NO
OBJECT_ID = NO
FILTER_COLUMNS = NO
SEQUENCE = NO
INCLUDE_NEW_VALUES = NO

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.

Materialized view log and user....

Hi,
Assume that a user , let's call him A owns a table and another user B needs to create a materialized view log on the table who owns the A user.
Whereas the user B do have all object privileges(direct priv insert, update, delete.. not via a role) on the table of user A he cannot create a mv log on this table on his schema....
So, the stmts insert/update/delete on <tab_name> are successfully executed (having connected as user B).
The error message "ORA-00942: table or view does not exist " appears when i issue the command:
connect B/B;
create materialized view log on tab_name with sequence including new values;
Note: I use ORADB 10.2.0.4 and there is a synonym of tab_name to the user B (who tries to create the mv log on)...
Is the above req. possible in any way...???
Thank you,
Sim

The documentation says the following:
The materialized view log is created in the same schema as the target master.HTH!

Create materialized view log with rowid hangs indefinitely..

Hi
create materialized view log on advice_note with rowid;
This stmt hangs indefinitely...
Help needed in resolving this issue
Rp

i have resolved the issue myself.
Found out the sessions that are locking the object , killed all those sessions & pids.
Rp

Materialized View Log

Hi,
I would like to create Fast refresh Materialized View in owb
Create Materialized View F_CALL_DAY_MV PARALLEL LOGGING BUILD IMMEDIATE REFRESH FAST ENABLE QUERY REWRITE AS
SELECT
FCALL.ACCOUNT_DIM_ID,
FCALL.INVOICE_DIM_ID,
FCALL.SCHEDULER_DIM_ID,
FCALL.CHAIRPERSON_DIM_ID,
FCALL.DATE_DIM_ID,
FCALL.RESERVATION_DIM_ID,
FCALL.PRODUCT_DIM_ID,
FCALL.CALL_STATUS_DIM_ID,
FCALL.REVENUE_CENTER_DIM_ID,
FCALL.CAMPAIGN_DIM_ID,
FCALL.SALESPERSON_DIM_ID,
count(*),
count (FCALL.CAMPAIGN_ELAPSED_DAYS_TO_CALL) cnt_CAMP_ELAPSED_DAYS_TO_CALL,
AVG(FCALL.CAMPAIGN_ELAPSED_DAYS_TO_CALL) AVG_CAMP_ELAPSED_DAYS_TO_CALL,
SUM(FCALL.SCHEDULED_CONNECTIONS) SCHEDULED_CONNECTIONS,
SUM(FCALL.ACTUAL_CONNECTIONS) ACTUAL_CONNECTIONS,
DDATE.THE_DATE,
DDATE.YEAR_NUM,
DDATE.MONTH_NUM,
DDATE.WEEK_OF_THE_YEAR,
DACCOUNT.BILL_ACCOUNT_CD,
DACCOUNT.ACCOUNT_NM,
DCHAIRPERSON.CONTACT_FULL_NAME,
DCHAIRPERSON.CONTACT_FULL_ADDRESS,
DCHAIRPERSON.MAIN_PHONE_NUM,
DCHAIRPERSON.MOBILE_PHONE_NUM,
DCHAIRPERSON.EMAIL_ADDR
FROM F_CALL FCALL,
D_ACCOUNT DACCOUNT,
D_CALL DCALL,
     D_INVOICE D_INVOICE,
     D_SCHEDULER DSCHEDULER,
     D_CHAIRPERSON DCHAIRPERSON,
     D_DATE DDATE,
     D_RESERVATION DRESERVATION,
D_PRODUCT DPRODUCT,
     D_CALL_STATUS DCALLSTATUS,
     D_REVENUE_CENTER DREVENUECENTER,
     D_CAMPAIGN DCAMPAIGN,
     D_SALESPERSON DSALESPERSON
WHERE FCALL.ACCOUNT_DIM_ID = DACCOUNT.ACCOUNT_DIM_ID
AND FCALL.CALL_DIM_ID = DCALL.CALL_DIM_ID
AND FCALL.INVOICE_DIM_ID = D_INVOICE.INVOICE_DIM_ID
AND FCALL.SCHEDULER_DIM_ID = DSCHEDULER.SCHEDULER_DIM_ID
AND FCALL.CHAIRPERSON_DIM_ID = DCHAIRPERSON.CHAIRPERSON_DIM_ID
AND FCALL.DATE_DIM_ID = DDATE.DATE_DIM_ID
AND FCALL.RESERVATION_DIM_ID = DRESERVATION.RESERVATION_DIM_ID
AND FCALL.PRODUCT_DIM_ID = DPRODUCT.PRODUCT_DIM_ID
AND FCALL.CALL_STATUS_DIM_ID = DCALLSTATUS.CALL_STATUS_DIM_ID
AND FCALL.REVENUE_CENTER_DIM_ID = DREVENUECENTER.REVENUE_CENTER_DIM_ID
AND FCALL.CAMPAIGN_DIM_ID = DCAMPAIGN.CAMPAIGN_DIM_ID
AND FCALL.SALESPERSON_DIM_ID = DSALESPERSON.SALESPERSON_DIM_ID
GROUP BY
FCALL.ACCOUNT_DIM_ID,
FCALL.INVOICE_DIM_ID,
FCALL.SCHEDULER_DIM_ID,
FCALL.CHAIRPERSON_DIM_ID,
FCALL.DATE_DIM_ID,
FCALL.RESERVATION_DIM_ID,
FCALL.PRODUCT_DIM_ID,
FCALL.CALL_STATUS_DIM_ID,
FCALL.REVENUE_CENTER_DIM_ID,
FCALL.CAMPAIGN_DIM_ID,
FCALL.SALESPERSON_DIM_ID,
DDATE.THE_DATE,
DDATE.YEAR_NUM,
DDATE.MONTH_NUM,
DDATE.WEEK_OF_THE_YEAR,
DACCOUNT.BILL_ACCOUNT_CD,
DACCOUNT.ACCOUNT_NM,
DCHAIRPERSON.CONTACT_FULL_NAME,
DCHAIRPERSON.CONTACT_FULL_ADDRESS,
DCHAIRPERSON.MAIN_PHONE_NUM,
DCHAIRPERSON.MOBILE_PHONE_NUM,
DCHAIRPERSON.EMAIL_ADDR
For this i need to create Materialized View Log as specified below for all the tables
used for creating above MV
CREATE MATERIALIZED VIEW LOG ON D_SALESPERSON
WITH ROWID, SEQUENCE(SALESPERSON_DIM_ID)
INCLUDING NEW VALUES;
But i'm not able to create MV log in oracle warehouse builder as specified above. When i specify base tables in owb it creates default mv log as
CREATE MATERIALIZED VIEW LOG ON D_SALESPERSON but i need to create MV log with "WITH ROWID, SEQUENCE(SALESPERSON_DIM_ID)
INCLUDING NEW VALUES"
Please could you help me to resolve this issue
Thanks
Kavitha

Hi,
I would just create the MV Log manually from SQL*Plus.
Best regards,
Erik

Materialized View Log table with sequence

I have a materialized view log in Database A..a very simple one...similar to "create materialized view log on t WITH PRIMARY KEY"...The primary key is a composite key of 2 columns...Description of the mlog table looks like this...
desc mlog$_t
emp_ctr NUMBER
emp_date DATE
SNAPTIME$$ DATE
DMLTYPE$$ VARCHAR2(1)
OLD_NEW$$ VARCHAR2(1)
CHANGE_VECTOR$$ RAW(255)
The Materialized view is in database B...again a simple one...no aggregation...This gets refreshed on demand manually evey week. The records that get accumulated in the MLOG every week is ~ 300K..The manual refresh used to finish in about 20mins but since last week it is running for ever. Upon reviewing the contents of MLOG I noticed that it contained a mixture of inserts and updates. I'm not sure if the MLOG contanied only inserts in the past when the MV used to refresh very quickly...Based on the documentation, Oracle recommends creating MLOGS with "sequence" whenever inserts/updates/deleted are expected. I'm planning to drop and recreate the MLOG with sequence with the hope that this would fix the slow refresh issue...Appreciate if you could let me know your thoughs...
I'm also planning to trace the session to get some wait event statistics to find out the reason for the slow refresh...

There are a few reasons why refreshes slow down over time.
1. Is the log table being cleared out after a refresh? If not, you may have another mview (maybe even one that doesn't exist any more) registered against this log. When this happens, the log table never stops growing.
2. How big is the segment occupied by the table? If it has grown very large at some time in the past (e.g., because refresh was delayed), then when the refresh does a FTS on the log it will scan the whole segment - even if only a few rows are present.
3. It may help to add an index to the PK columns, and another to SNAPTIME$$. Without them, the refresh will FTS the log. For a big segment, that can take a long time.
-- Phil

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

Materialized View Logs on OLTP DB- Performance issues

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