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

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Question on Materialized View Log Table

Hello,
One of our MLOG table keeps growing without the records getting flushed out ...The Materiazed view gets refreshed successfully though...The master/mlog tables are remote..
There is only one MV attached to the master table as evident from the results below...
//On the Master site
select owner,name, mview_site, mview_id from all_registered_mviews where owner='SSP' and name='TRANS_STATUS'
Owner Name MVIEW_SITE MVIEW_ID
SSP TRANS_STATUS SSPRD     12864
The above output is expected and good but I was surprised to see the output below...
select owner,master,to_char(mview_last_refresh_time,'MM-DD-YYYY HH:MI:SSAM'), mview_id from all_base_table_mviews where owner='SSP' and master='TRANS_STATUS'
Owner Master MVIEW_LAST_REFRESH_TIME MVIEW_ID
SSP TRANS_STATUS     01-27-2011 06:32:05PM     12724
SSP TRANS_STATUS     01-29-2011 12:03:06PM     12844
SSP TRANS_STATUS     06-18-2011 07:32:55AM     12864
I'm not sure why I see differnt MVIEW_IDs...We refresh this MV every day....
On 01-27-2011 it was a regular normal refresh using dbms_mview.refresh
On 01-29-2011 we had to drop and recreate our MV and then refresh it using dbms_mview.refresh
On 06-18-2011 it was a regular normal refresh using dbms_mview.refresh
Why are there different MVIEW_IDs when there is only one MV that is attached to the master table. Could this be the reason why the logs are not getting flushed out?
Thanks for your time...

What is your database version?
How did you even manage to create two objects with the same name?
As I know, it is impossible, oracle will throw errors like below:
SQL> create table FOO (str varchar2(5), num number(3,0));
Table created.
SQL> CREATE MATERIALIZED VIEW FOO
2 BUILD DEFERRED
3 REFRESH COMPLETE ON DEMAND
4 enable query rewrite as
5 select SUM(NUM)
6 from FOO GROUP BY STR;
from FOO GROUP BY STR
ERROR at line 6:
ORA-00955: name is already used by an existing object
SQL>

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 logs pretty huge!

Hi,
I have a table MLOG$_XXXXX, which i guess is a materialized view log table. It is huge in size (80GB) and is growing at a very alarming rate.
Could someone please help me to reduce the size of this table?
How do I find out which materialized view is causing this table to grow? Is there any query through which I can find this out?
The database is of version 10204 and is running on HP Unix (B.11.11).
Thanks!

The materialized views in the database are:
SQL> select mview_name, owner, updatable, refresh_mode, last_refresh_date from dba_mviews;
MVIEW_NAME                     OWNER      U REFRESH_MODE    LAST_REFRESH_DATE
MV_EXCH_RT                     SYS        N COMMIT          03 JUN 2010 12:02:59
ADMIN_MGMT_CO                  JJORA      N DEMAND          06 JUL 2010 01:37:39
REG                            JJORA      N DEMAND          06 JUL 2010 01:37:39
CNTRY                          JJORA      N DEMAND          06 JUL 2010 01:37:39
OPER_GRP                       JJORA      N DEMAND          06 JUL 2010 01:37:39
ADMIN_CO                       JJORA      N DEMAND          06 JUL 2010 01:37:39
MV_JJGL_SUB_CD_141P            JJGL       N DEMAND          06 JUL 2010 01:24:43
7 rows selected.The table which grows at an alarming rate is:
SQL> select sum(bytes)/1024/1024/1024 from dba_segments where segment_name like 'MLOG$_XXXXX%';
SUM(BYTES)/1024/1024/1024
               77.8789063Now how do I find out, which materilized view is causing this table to grow? Can someone please provide me the query?
Thanks!
Edited by: user9104898 on Jul 6, 2010 8:11 AM

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

Help with sql query on materialized view logs

I am in need of a query to find out what tablespace and snap shot site a long list of materialized view logs are associated with.
something like below except tablespace and snap_shot_site are not an option for this table.
select log_owner, master, log_table, tablespace, snap_shot_site from dba_mview_logs;

What is the refresh method set as?
Could you paste the full MV log creation script and the corresponding MV creation script.

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.

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.

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 log VS Trigger to trace table changes !

Hi All
I have to trace changes on couple tables and only those changes then send to other system.
What do you think is better solution to create a Status table and update it via trigger.
I saw that MV log can be used for such purpose, but I am not able to create a MV logging on more than one table.
Or is there any other more effective way to trace changes on table?
Thanks a lot
Martin

It sounds like you should be looking at something like Change Data Capture (CDC). You could also create materialized view logs on each table where you wanted to track changes, create appropriate materialized views on the remote database, and consume the data there. It really depends on what exactly you want to do with the changes you're tracking.
Justin

Whats the purpose of materialized view log?whats create view log with rowi

Why we create materialized view log ?????whats the use???
what do you mean by "create view log with rowid"
Regards
Gagan

A materialized view log stores the change vectors made to a particular table in order to allow materialized views that reference that table to be incrementally refreshed rather than re-materializing the data every time. It's a much more efficient way to refresh a materialized view.
WITH ROWID specifies that the materialized view log should store the ROWID of a row with the change vector, which is one way of identifying which row(s) in the materialized view should be updated by which change vector. You can also use the primary key value for this.
Justin

ORA-12096: error in materialized view log on a table

Hi while updating a table getting below error
ORA-12096: error in materialized view log on "FII"."FII_GL_JE_SUMMARY_B"
What might be the problem.
Thanks.

might be table definition has changed, you may need to drop the mview log and recreate it.

Materialized view log with multiple materialized views

DB: 9.2.0.8
Yes its old. I am not allowed to upgrade it.
I have a set of materialized views that are created off of 5 base tables. They do fast refreshes. So I have multiple materialized views for the same base table and same materialized view log.
1. how do materialized view logs manage multiple dependent materialized views?
2. How do I tell by looking at the materialized view log which rows have not been fast refresh for a specific materialized view?

As a starter for 10 try reading: Materialized View Refresh : Log Population and Purge (Doc ID 236233.1) on MOS.
Thanks
Paul

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

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 table with sequence

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