Questions on Materialized Views and MV Log tables

Hello all,
Have a few questions with regards to Materialized View.
1) Once the Materialized View reads the records from the MLOG table the MLOG's records get purged. correct? or is it not the case? In some cases I still see (old) records in the MLOG table even after the MV refresh.
2) How does the MLOG table distinguish between a read that comes from an MV and a read that comes from a user? If I manually execute
"select * from <MLOG table>" would the MLOG table's record get purged just the same way as it does after an MV refresh?
3) One of our MV refreshes hangs intermittently. Based on the wait events I noticed that it was doing a "db file sequential read" against the master table. Finally I had to terminate the refresh. I'm not sure why it was doing sequential read on the master table when it should be reading from the MLOG table. Any ideas?
4) I've seen "db file scattered read" (full table scan) in general against tables but I was surprised to see "db file sequential read" against the table. I thought sequential read normally happens against indexes. Has anyone noticed this behaviour?
Thanks for your time.

1) Once all registered materialized views have read a particular row from a materialized view log, it is removed, yes. If there are multiple materialized views that depend on the same log, they would all need to refresh before it would be safe to remove the MV log entry. If one of the materialized views does a non-incremental refresh, there may be cases where the log doesn't get purged automatically.
2) No, your query wouldn't cause anything to be purged (though you wouldn't see anything interesting unless you happen to implement lots of code to parse the change vectors stored in the log). I don't know that the exact mechanism that Oracle uses has been published, though you could go through and trace a session to get an idea of the moving pieces. From a practical standpoint, you just need to know that when you create a fast-refreshable materialized view, it's going to register itself as being interested in particular MV logs.
3) It would depend on what is stored in the MV log. The refresh process may need to grab particular columns from the table if your log is just storing the fact that data for a particular key changed. You can specify when you create a materialized view log that you want to store particular columns or to include new values (with the INCLUDING NEW VALUES) clause. That may be beneficial (or necessary) to the fast refresh process but it would tend to increase the storage space for the materialized view log and to increase the cost of maintianing the materialized view log.
4) Sequential reads against a table are perfectly normal-- it just implies that someone is looking at a particular block in the table (i.e. looking up a row in the table by ROWID based on the ROWID in an index or in a materialized view log).
Justin

Similar Messages

Question on MATERIALIZED VIEW and table

HI
there are table (name is test123) and MATERIALIZED VIEW (name also is test123) stored in the same schema (name is schema123).
If I run sql : select from schema123.test123;*
I wanna know the result data I get is data of table test123 or MATERIALIZED VIEW test123, which one of them?
Thanks in advance!

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>

Who can help to solve this question on MATERIALIZED VIEW and table?thanks

Hi,dear all.
If there is a MV with the same name as a table and they both exist in the same schema .
e.g: MV : test123 and table : test123 (they have same name) exist in schema : schema123.
when I run a sql : select * from schema123.test123; , what's the result of the execution?? MV or table which of them's data are populated???
thanks in advance!

solved.

Updatable Materialized View and Master Table on same database

Hi all,
My first question - Is it possible to have an Updatable Materialized View and the associated Master Table located on the same database?
This is the requirement scenario:
One unique database D exists.
A is a batch table. Only inserts are allowed on Table A.
M is an updatable materialized view on Table A (Master). Only updates are allowed on M (no insert or delete).
Requirement is to push updates/changes from M to A periodically and then get the new inserted records from A into M via a refresh.
Is this possible? What other approaches are applicable here?

John,
My question is related to the implementation and setup of the environment as explained in the above example. How can I achieve this considering that I have created an updatable m-view?
If possible, how do I push changes made to an updatable m-view back to it's master table when/before I execute DBMS_MVIEW.REFRESH on the m-view? What is the procedure to do this if both table and mview exist on the same database? Do I need to create master groups, materialized view refresh groups, etc.?
One more thing.. Is there a way to retain changes to the m-view during refresh? In this case, only newly inserted/updated records in the associated table would get inserted into m-view. Whereas changes made to m-view records would stay as-is.
Hope my question is directed well. Thanks for your help.
- Ankit

Materialized View and Ord Media questions

Hey Guys,
My first question is on the use and creation of materialized views which i have previously done using TOAD. The question that i have is where/if can i visually see the constraints that are on a materialized view and where is the information for "next refresh" times placed?
Question two is about viewing informaiton on ord media objects that are stored. Previously, i had the ability to double click one of these elememts in the data view and see the information related to that instance of the ord media object, but the SQL developer does not seem to have this ability??
Thanks in advance.

Thanks Kris,
The reason that i asked about the constraints on MV is because when you create a materialized view over a db link with primary key, it will place a not null constraint on every column. This is obviously no good because some rows are bound to contain nulls and these need to be removed and updated before it will work!
As for the ord objects, it just makes it a little easier for testing to see what they are :).
Anyway, its looking great and i hope these features will be in the next release?
Cheers David

Materialized view and Partition

Hi,
I want to discuss a scenario, with which i am dealing nowadays. there is only a single table (named livecdr ) has 22-23 fields and the records are updating in every sec (on daily basis) and in 24hrs livecdr contains approximately more than 2 crore records.
Problem is that the query processing time is so slow due to large number of records and query is fetching records from a view created on livecdr table. I want to know the options, how the query would fetch these records in a short time. Firstly i did range partitioning on livecdr and then i created materlized view but the view didn't create on partition table and when i removed partitioning it was created. After view creation, query performance is much better. i also applied indexing on livecdr.
Can you please tell me, whether this approach is okay or i am doing mistake. should i create partitioning on materialized view and how would i select records from view if partitioning would be applied on materialized view. Please guide me with best approaches.
thankyou.

Hello,
Here is how I created partitioned table (monthly partitions) and partitioned mview on the table. This is just an example you might have to change the mview partitions from monhtly to yearly or quartely.
CREATE TABLE live_cdr
   CALLID              VARCHAR2 (20),
   CD                  VARCHAR2 (25),
   CG                  VARCHAR2 (25),
   RE                  VARCHAR2 (25),
   OPC                 VARCHAR2 (12),
   DPC                 VARCHAR2 (12),
   STIME               VARCHAR2 (25),
   SDATE               DATE,
   ATIME               VARCHAR2 (25),
   ADATE               DATE,
   ETIME               VARCHAR2 (25),
   EDATE               DATE,
   schangeTime         VARCHAR2 (25),
   schangeDate         DATE,
   STATUS              VARCHAR2 (25),
   bucket              NUMBER (20),
   CIC                 NUMBER (20),
   charge              VARCHAR2 (30),
   ported              VARCHAR2 (30),
   jurisdiction_Info   VARCHAR2 (30),
   origLine_Info       CHAR (1),
   Variant             NUMBER,
   auto_inc            NUMBER
PARTITION BY RANGE (EDATE)
PARTITION LIVE_CDR_JAN_2009 VALUES LESS THAN (TO_DATE(' 2009-02-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN'))
    LOGGING
    NOCOMPRESS,
PARTITION LIVE_CDR_FEB_2009 VALUES LESS THAN (TO_DATE(' 2009-03-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN'))
    LOGGING
    NOCOMPRESS
);Mview definition
CREATE MATERIALIZED VIEW KLONDIKE.LIVE_CDR_MV
LOGGING
PARTITION BY RANGE (EDATE)
PARTITION LIVE_CDR_MV_JAN_2009 VALUES LESS THAN (TO_DATE('20090201',
      'YYYYMMDD'))
    LOGGING
    NOCOMPRESS,
PARTITION LIVE_CDR_MV_FEB_2009 VALUES LESS THAN (TO_DATE('20090301',
      'YYYYMMDD'))
    LOGGING
    NOCOMPRESS
BUILD IMMEDIATE
REFRESH COMPLETE
START WITH SYSDATE
NEXT SYSDATE + 2 /24
AS
SELECT   DISTINCT (ic.callid) callid,
                  ic.CG,
                  ic.CD,
                  ic.RE,
                  ic.OPC,
                  ic.DPC,
                  ic.SDATE,
                  ic.STIME,
                  ac.ADATE,
                  ac.ATIME,
                  ec.ETIME,
                  ec.EDATE,
                  ec.STATUS
FROM   live_cdr ic, live_cdr ac, live_cdr ec
WHERE       ic.callid = ac.callid
         AND ic.callid = ec.callid
         AND ic.stime = ac.stime
         AND ic.stime = ec.stime
         AND ic.sdate = ac.sdate
         AND ic.sdate = ec.sdate
         AND ac.ADATE IS NOT NULL
         AND ec.EDATe IS NOT NULL
         AND ec.etime IS NOT NULL
         AND ic.CD IS NOT NULL
         AND ic.cg IS NOT NULL;Regards

Materialized View with No Logging Option;;; THX

Hi all,
What's the diffrence between a :
Materialized View with No Logging Option
Materialized View with Logging Option
thank you

LOGGING|NOLOGGING specifies that subsequent Direct Loader (SQL*Loader) and direct-load INSERT operations against a nonpartitioned index, a range or hash index partition, or all partitions or subpartitions of a composite-partitioned index will be logged (LOGGING) or not logged (NOLOGGING) in the redo log file.
In NOLOGGING mode, data is modified with minimal logging (to mark new extents invalid and to record dictionary changes). When applied during media recovery, the extent invalidation records mark a range of blocks as logically corrupt, because the redo data is not logged. Therefore, if you cannot afford to lose this index, you must take a backup after the operation in NOLOGGING mode.
If the database is run in ARCHIVELOG mode, media recovery from a backup taken before an operation in LOGGING mode will re-create the index. However, media recovery from a backup taken before an operation in NOLOGGING mode will not re-create the index.
An index segment can have logging attributes different from those of the base table and different from those of other index segments for the same base table.
Message was edited by:
HAGGAR

Materialized View and I_SNAP$ Indexes

Hello Everybody,
At the time of doing REFRESH of the Materialized View, we are getting error like -
SQL> EXECUTE DBMS_MVIEW.REFRESH('MV_TEST.MY_VIEW,'CF');
BEGIN DBMS_MVIEW.REFRESH('MV_TEST.MY_VIEW,'CF'); END;
ERROR at line 1:
ORA-12008: error in materialized view refresh path
ORA-00001: unique constraint (MV_TEST.I_SNAP$_FIN_RESULT_EXPENSE1) violated
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 2545
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 2751
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 2720
ORA-06512: at line 1
I tried to drop and recreate the index I_SNAP$_FIN_RESULT_EXPENSE1 but it didn’t helped.
Later I dropped the index I_SNAP$_FIN_RESULT_EXPENSE1 and refreshed the materialized view and it was successful (obvious). But when I tried to recreate the index, I got the following error –
SYS_OP_MAP_NONNULL("FIN_MULT"), SYS_OP_MAP_NONNULL("FIN_CD"))
ERROR at line 8:
ORA-01452: cannot CREATE UNIQUE INDEX; duplicate keys found
When I look at the value of SYS_OP_MAP_NONNULL('FIN_CD'), it seems to be unique.
SQL> select SYS_OP_MAP_NONNULL('FIN_CD') from dual;
SYS_OP_MAP_NONNULL('FIN_CD’)
46494E5F5650545F4C564C5F335F434400
My questions are:
1.     Why are the indexes (I_SNAP$_*) automatically created for?
2.     What is the purpose of these (I_SNAP$_*) indexes?
3.     What harm can be there if we drop these (I_SNAP$_*) indexes?
4.     Why it is complaining about the Duplicate records / Uniqueness?
5.     How to know where exactly the problem is in this case?
6.     What is the solution for this problem? How to recreate these indexes successfully?
Thanks!

Hello Rafi,
I don't have any MLOG$_<table> in the database, After connecting as SYS -
SQL> select tname from tab where tname like '%MLOG%';
TNAME
MLOG_REFCOL$
MLOG$
C_MLOG#
SQL> select count(*) from mlog$;
COUNT(*)
0
I am not using Replication here -
SQL> select tname from tab where tname like '%RUPD%';
no rows selected
Why you think that granting SELECT access to MLOG$_* tables will solve this issue?
Thanks,
Roopesh

Materialized view or a big table

Hi all,
In our project based on Documentum we are expecting to store 140 million of invoices of third party consultant companies in our Oracle 10g database. We received two different approaches from data modeling team.
First is in order to speed up the queries to “denormolize” the data and store to the one table which will have 140 million of records with the total length 403 bytes or to split it in two tables Company and Invoice.
In this case the Company table will contain 2000000 of records X 116 bytes and Invoice table 140 million of records X 171 byte. They also suggested creating the materialized view based on those two tables to take advantage of “fast refresh” feature.
I don’t have any experience with materialized views and my question is what is which of those approaches is the best
Any suggestion will be much appreciated.
Thanks in advance,
Alex

I'd say that it mostly depends on other requirements at least including:
1) how many changes (inserts/updates) do you expect? Especially in spike hours.
2) how fast you'd like to see changes in the Mat view if you choose this approach? ON COMMIT? On regular interval basis? If on commit then if you predict to have problems with performance in spike hours (see above) then you'll have even more problems because on commit is rather expensive in terms of total statements executed (see tables under Bright idea – materialized views in http://www.gplivna.eu/papers/mat_views_search.htm)
3) how big is the possibility and will you have a requirement at all to update existing companie's data in already registered invoices?
4) What kind of queries you'll have and do at least some of them benefit from 2 table approach i.e. could be satisfied only with companies table?
Gints Plivna
http://www.gplivna.eu

Problems with materialized view and fk between two db

Hi,
i have two databases db1 and db2 and from db1 is a table(DM_MESSDATEN) which contains a foreign key to a table(DM_FAUNA) in db2.
Now I want to write my done steps to get more clearification and hopefully someone can point out my wrong steps.
1st
i create the tables inside db1 without a foreign key to the table in db2.
2nd
i create a database link inside db1 to db2
create public database link DATENBANK2 connect to phantomas identified by bachelor06 using 'DMDB2';
3rd
now and here i stuck want to create a materialized view inside db1
create materialized view DATAMART_MVW AS
select * from DM_MESSDATEN, DM_FAUNA@DATENBANK2
where DM_MESSDATEN.FAUNA_ID=DM_FAUNA.FAUNA_ID;
or should the view be created inside of db2?
4th
and then i want to reactivate the foreign key inside the table of db1- but can't because of
problems in step 3 :(
So it would be nice if someone could help me
thanks a lot
thomas

I think you haven't been clear in your statement of your problem:
now and here i stuck want to create a materialized view inside db1Why are you stuck? If you want to enforce a froeign key locally using data from a remote database then you need to build a materialized view on your local table tablespace that sucks data across from the remote database. You can then create a foreign key on your local table using the local MV.
If the remote table is updated frequently and you want the local MV kept in sync then you will need to put soem further replication in place. For instance you may need to create a materilaized view log on the remote database.
Cheers, APC

Materialized view and policies

Hello,
We created an materialized view and on this view why created a policy.
SYS.DBMS_RLS.ADD_POLICY
Now we added some values to the MV via drop MV and create MV.
The policy on this MV is gone after the drop statement.
Is there away to secure this?
Thanks,
Remco

Why are you dropping and re-creating the materialized view in the first place? That's not something that should ever happen in a live system. You should just be refreshing the data in the materialized view, in which case the privileges & policies associated with the materialized view would be retained. It's no different than dropping and re-creating a table that has a policy associated with it-- you'd have to re-apply the policy after re-creating the table.
Theoretically, I suppose you could create a DDL trigger that would throw an error if you tried to drop an object with an associated policy. Fixing your approach, though, so that you're not dropping & re-creating objects is going to be the better long-term solution.
Justin

Diff materialized view and view

what is diff materialized view and view

Check these documents please
[Overview of Materialized Views|http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/schema.htm#CNCPT411]
[Overview of Views|http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/schema.htm#i20690]
Kamran Agayev A. (10g OCP)
http://kamranagayev.wordpress.com

Materialized view and snapshot

Hi gurus,
Could you please tell me what is the difference between materialized view and snapshot.
Regards
Koustav

A snapshot, is in general terms, a picture, a click of a camera, an image that captures the position/state of something at sometime.
Snapshot in a database can take many points of view.
Materialized view (MV) is an object in Oracle database. It "materializes" a view, by taking a snapshot, of the view when you actually create the MV, and preserve it for future use. It can be refreshed in several available ways.
A view doesn't occupy any space, a MV does.
HTH,
Aswin.

Need detailed info about Active,New and Change log table in BI 7.0

Dear Experts,
I am new to this technology. Can you any one explain in very detail about ACTIVE, NEW and CHANGE LOG tables workflows.
And also i am requesting you all to give tips to how to study BI 7.0
Regards,
Ameer.N

For your first problem solution is this note: 936644
You might have not mapped the filed in your tarnsfer/update rules?

Need to get a list of PSA tables and change log tables existing in a PC

Is there a standars table to look up all active DSOs and the change log tables associated to those DSOs?
and also Data sources and the PSA tables associated to that DS.
I need to get a list of PSA tables and change log tables existing in a processchain(whioch deletes the data in them time to time)how do I do this in a quicker way?
Thanks in advance

Hi Ramya
Check RSTSODS table with filter of User App CHANGELOG ---> For change log tables

Questions on Materialized Views and MV Log tables

Similar Messages

Maybe you are looking for