Configure archiver to read from both redo log members
Hi, We have moved our Data Warehouse to a new SAN. The luns for the redo logs are getting hit heavily. Just trying to find out if on AIX it is possible to configure archiver so that it reads from both members, current iostat data shows reads of the redo logs are only happening against the first member of each group and none against the second member. Thanks Tom Cullen
See a recent discussion on this issue :
Redo log Doubt
Hemant K Chitale
Similar Messages
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Archive all the active online redo logs
Hi,
in 9.2.0 and in archivelog mode, how can I archive all the active online redo logs ?
Thank you.Is ur database already running in archivelog mode?? If yes and if automatic archiving is enabled then ur redo will be archived automatically. I think first you need to check whether ur DB is in archive log mode or not?? Post the output of (from sqlplus):
archive log list
Daljit Singh -
Hello!
Could you please explain , is the filling of redo log members async or sync?
Thanks and regards,
PavelPavel wrote:
Hello!
Could you please explain , is the filling of redo log members async or sync?
Yes, the filling of redo log members is async or sync.
For example, on exadata, redo can be written to both SSD and hard disk, and whichever is done first is sync, and the other isn't.
On DG, you can do it either way.
If you look at the various internal mechanisms for private redo strands, you can have several situations.
[url http://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:60447282988010]You can also have async commits, as [url http://asktom.oracle.com/pls/asktom/f?p=100:11:::::P11_QUESTION_ID:1415454871121#20061201507022]PL/SQL has done since forever.
See also http://www.pythian.com/news/1098/tuning-log-file-sync-event-waits/ -
How to recover from corrupt redo log file in non-archived 10g db
Hello Friends,
I don't know much about recovering databases. I have a 10.2.0.2 database with corrupt redo file and I am getting following error on startup. (db is non archived and no backup) Thanks very much for any help.
Database mounted.
ORA-00368: checksum error in redo log block
ORA-00353: log corruption near block 6464 change 9979452011066 time 06/27/2009
15:46:47
ORA-00312: online log 1 thread 1: '/dbfiles/data_files/log3.dbf'
====
SQL> select Group#,members,status from v$log;
GROUP# MEMBERS STATUS
1 1 CURRENT
3 1 UNUSED
2 1 INACTIVE
==
I have tried this so far but no luck
I have tried following commands but no help.
SQL> ALTER DATABASE CLEAR UNARCHIVED LOGFILE GROUP 3;
Database altered.
SQL> alter database open resetlogs;
alter database open resetlogs
ERROR at line 1:
ORA-01139: RESETLOGS option only valid after an incomplete database recovery
SQL> alter database open;
alter database open
ERROR at line 1:
ORA-00368: checksum error in redo log block
ORA-00353: log corruption near block 6464 change 9979452011066 time 06/27/2009
15:46:47
ORA-00312: online log 1 thread 1: '/dbfiles/data_files/log3.dbf'user652965 wrote:
Thanks very much for your help guys. I appreciate it. unfortunately none of these commands worked for me. I kept getting error on clearing logs that redo log is needed to perform recovery so it can't be cleared. So I ended up restoring from earlier snapshot of my db volume. Database is now open.
Thanks again for your input.And now, as a follow-up, at a minimum you should make sure that all redo log groups have at least 3 members. Then, if you lose a single redo log file, all you have to do is shutdown the db and copy one of the good members (of the same group as the lost member) over the lost member.
And as an additional follow-up, if you value your data you will run in archivelog mode and take regular backups of the database and archivelogs. If you fail to do this you are saying that your data is not worth saving. -
Behaviuor in reading logs from DB13 - redo log backup for DB
Hi all,
I have a question ,
We have scheduled redo log backup using HP DP Tool.
When I am reading a backup log from DB13 , I am facing the weird behavior.
copy, delete, save
0000
aeomzyok.cds
copy, delete, save
0001
aeomzyoh.cds
Where ever the RC is 000 I am able to read the log files available at OS level . But not able to read the log for other RC.
Please help me to understand this
Thanks,
GnanaHi Gnana.
Use the latest BR*Tools as there were problems with permission issues while creating logfiles. In the latest BR*Tools version, the different logfiles are created with predefined permission levels that suits to SAP needs.
Also it worth to check if the BR*Tools executables hav the correct ownership.
113747 Owners and authorizations for BR*Tools
Regards,
János -
Read from both load cell and accelerome​ter
Hi,
I'm trying to collect data from both load cell (which doesn't need excitation) and accelerometer (which needs 4 mA excitation). As you can see below, I wrote a simple program to collect data from both devices. However, my program provides 4 mA of excitation to all channels, one of which shouldn't receive any current. How can I selectively provide the excitation to specific channels?
Any suggestions?
Solved!
Go to Solution.
Attachments:
readfromtwodevices.vi 47 KBGood morning jeongho20000,
Both aeastat and falkpl have provided excellent solutions for this. I also wanted to mention a good KnowledgeBase article found at ni.com by searching for "daqmx channel same task" in the internal search bar. This helps to outline both solutions. After searching, you can then select multiple entries, but the best that I found was the 3rd choice, titled: Using Different Types of DAQmx Global Channels in the Same Task.
You can download from the article the attached example VI titled Multiple Channels Created.vi, and modify the block diagram to fit your needs. Wiring the Task Out to the Task In of two DAQmxCreateChannel VIs is the programmatic equivalent of adding multiple Global Virtual Channels created in Measurement and Automation Explorer (MAX) to a common Task in MAX. Either method works, it is only a user preference. Feel free to reply if you need further clarification/explanation.
Best,
Message Edited by cyclone2k9 on 04-06-2010 11:08 AM
Message Edited by cyclone2k9 on 04-06-2010 11:09 AM
Adam
Academic Product Manager
National Intruments -
Hi i have a couple of questions
1) what is the max value i can set for MAXLOGFILES in controlfile? that is maximum how many redo log groups i can have in a database(when not considering space occupied by log members)
2) I had a 2 log groups with 2 members in each. how LGWR writes into log members of each group. whether it will done in serial(sequential order) or parallel? If it is sequential, when LGWR writes into 2nd member of one group if i perform a log switch, will it wait till it completes writing into that member and switches to another group?
thanks in advance>>> I had a 2 log groups with 2 members in each. how LGWR writes into log members of each group. whether it will done in serial(sequential order) or parallel? If it is sequential, when LGWR writes into 2nd member of one group if i perform a log switch, will it wait till it completes writing into that member and switches to another group?
Mr.Howard Rodger wrote:-
There is only ever one Log Writer process. Unlike Database Writer, for example, which can have several 'clone' processes sharing the work burden, redo log records must be written to disk sequentially -and that means only one process can be in charge of working out what to write to disk. If that wasn't true, you might come to grief when a series of transactions have dependencies. If you first create a new product record and then raise a new sale record to indicate that the new product has just been sold, for example, you need the product transaction to be recorded before the sale transaction -otherwise, during a recovery, you might end up trying to sell a product that doesn't exist yet. To prevent that logical nonsense from happening, therefore, a single Log Writer process writes everything in the correct sequence.
I hope it helps
Regards
Nisanth V Santhan -
Hi,
My production database servers run on HP-XP storage, raid 5. Currently the redo logs are striped on 16 disks, as raw files. I use 5 groups, 2 members in each group.
I wanted to hear your opinion, if two members are still necessary with todays storage hardware, considering the mirroring already done in the hardware level.
What is the benefit today for having more than one member in a group, and do you think it's worth the IO price most of us are still paying...
Thanks in advance,
Idan.For example here:
http://asktom.oracle.com/pls/ask/f?p=4950:8:::::F4950_P8_DISPLAYID:359617936136
Try search google btw. There are plenty of articles.
Just if you read concepts of RAID you will learn that RAID 5 is not good for write intensive operations (redo logs are write intensive). -
hi
in Oracle documentation they said you can't drop a member if it's an active
but i tried it in Oracle's Database 10g and it's dropped successfully
what happend ?
The link is :
http://download.oracle.com/docs/cd/B28359_01/server.111/b28310/onlineredo005.htm
Thanks>
but i tried it in Oracle's Database 10g and it's dropped successfully >
You would have done alter system switch logfile before dropping the active redo logsfile.
Refer to the link for the status of the redo logs [http://download.oracle.com/docs/cd/B14117_01/server.101/b10755/dynviews_1126.htm#REFRN30127]
23:36:05 venture >select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIM
1 1 29 104857600 1 NO INACTIVE 7457724 07-DEC-08
2 1 30 104857600 1 NO INACTIVE 7794484 08-DEC-08
3 1 33 104857600 1 NO CURRENT 8016830 09-DEC-08
4 1 31 104857600 1 NO INACTIVE 8016825 09-DEC-08
5 1 32 104857600 1 NO INACTIVE 8016827 09-DEC-08
23:38:01 venture >create table test as select rownum id,'TEST' name from dual connect by level <= 10000000;
Table created.
Elapsed: 00:00:20.09
23:39:27 venture >select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIM
1 1 29 104857600 1 NO INACTIVE 7457724 07-DEC-08
2 1 30 104857600 1 NO INACTIVE 7794484 08-DEC-08
3 1 33 104857600 1 NO CURRENT 8016830 09-DEC-08
4 1 31 104857600 1 NO INACTIVE 8016825 09-DEC-08
5 1 32 104857600 1 NO INACTIVE 8016827 09-DEC-08
Elapsed: 00:00:00.00
23:39:34 venture >alter database drop logfile group 3;
alter database drop logfile group 3
ERROR at line 1:
ORA-01623: log 3 is current log for thread 1 - cannot drop
ORA-00312: online log 3 thread 1: 'D:\ORACLE\ORADATA\VENTURE\REDO03.LOG'
Elapsed: 00:00:00.01
23:39:51 venture >alter system switch logfile;
System altered.
Elapsed: 00:00:00.01
23:40:02 venture >select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIM
1 1 34 104857600 1 NO CURRENT 8017910 09-DEC-08
2 1 30 104857600 1 NO INACTIVE 7794484 08-DEC-08
3 1 33 104857600 1 NO ACTIVE 8016830 09-DEC-08
4 1 31 104857600 1 NO INACTIVE 8016825 09-DEC-08
5 1 32 104857600 1 NO INACTIVE 8016827 09-DEC-08
Elapsed: 00:00:00.00
23:40:03 venture >alter database drop logfile group 3;
alter database drop logfile group 3
ERROR at line 1:
ORA-01624: log 3 needed for crash recovery of thread 1
ORA-00312: online log 3 thread 1: 'D:\ORACLE\ORADATA\VENTURE\REDO03.LOG'
Elapsed: 00:00:00.00
23:40:11 venture >alter system switch logfile;
System altered.
Elapsed: 00:00:00.01
23:40:25 venture >select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIM
1 1 34 104857600 1 NO INACTIVE 8017910 09-DEC-08
2 1 35 104857600 1 NO CURRENT 8018022 09-DEC-08
3 1 33 104857600 1 NO INACTIVE 8016830 09-DEC-08
4 1 31 104857600 1 NO INACTIVE 8016825 09-DEC-08
5 1 32 104857600 1 NO INACTIVE 8016827 09-DEC-08
Elapsed: 00:00:00.00
23:40:28 venture >alter database drop logfile group 3;
Database altered.
Elapsed: 00:00:00.00
23:40:42 venture >select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIM
1 1 34 104857600 1 NO INACTIVE 8017910 09-DEC-08
2 1 35 104857600 1 NO CURRENT 8018022 09-DEC-08
4 1 31 104857600 1 NO INACTIVE 8016825 09-DEC-08
5 1 32 104857600 1 NO INACTIVE 8016827 09-DEC-08
Elapsed: 00:00:00.00
23:40:46 venture >HTH
Anand -
Hello-
I was looking at some old database installs and if the REDO logs are stored in the same file directory then isn't having two members
not very useful and only good for placing these on another file system ?
Thanks-Admin. Guide says http://download.oracle.com/docs/cd/E11882_01/server.112/e17120/onlineredo002.htm#ADMIN11309
>
To protect against a failure involving the redo log itself, Oracle Database allows a multiplexed redo log, meaning that two or more identical copies of the redo log can be automatically maintained in separate locations. For the most benefit, these locations should be on separate disks. Even if all copies of the redo log are on the same disk, however, the redundancy can help protect against I/O errors, file corruption, and so on. -
Hi,
I am running 10gRac on Linux
I have 4 groups with 1 member each (50MB).
The DB is running in noarchive mode
I heard there is recommendation to have at least 2 members in each group.
Now how can I check if I should add more members to the groups?
ThanksHi br00klynZ00,
just imagine that you loose the only member of an unarchive group.
Maybe teh CURRENT?!
What do you do then?
You habe lost data then if you have a crash in addition because you cannot recover your lost instance.
So you should definitely have at least two members for each group!
=;-)
Hope this clarifies a little what the problem is.
BR,
Lutz -
1. How can i read the DML's in the redo log?
I need the statements from the redo log like we get through LOGMINOR in SQL_REDO column.
2. How to create the archive log file from Redo logs through a command?
Means i want to clean the Redo log and want to create archive log so that i can use those archive log in LOGMINOR.
Thanks,Hemant K Chitale wrote:You can find out which row it is and what are the contents of that row currently in your database by querying
Once you get the values, you'd have to work backwards (or forwards) to figure out what values you need to set in the other database.Actually i also have other tables then how i can consider perticular column name and search that?I could have other statements.
update "TEST2" set "LEADCOUNTSTDFAILED" = '234' where "LEADCOUNTSTDFAILED" = '233' and ROWID = 'AAAQDRAAKAAAUSdAAs';
Then how i can get it.
Also that view conists of thousands of DML's.
Thanks, -
GoldenGate Extract Process will not read from redo log with manual help
Here is my issue.
I have GoldenGate replication successfully setup one-way from 1 Source to Many Targets. There is 1 source extract on the DB and many pumps that push the trail file data to the Targets. Replication does work but after manual help with starting up the Source Extract process.
If I execute the command:
GGSCI> alter extract <source extract name> begin now
GGSCI> view report <source extract name>
The extract starts and reads the source trail file but will not process data, I continually see in the ggserr.log file "OGG-01515: Positioning to begin time MMM DD, YYYY, HH:MM:SS" The date and time are irrevelant for this problem.
When I see this, I SQ*Plus into the database and look in the v$log table for the current log and sequence #.
I return to GGSCI and issue the following command:
GGSCI> alter extract <source extract name> thread 1 extseqno <sequence # from v$log query>
GGSCI> start <source extract name>
It then works as expected. Why is this so? I thought the alter extract <source extract name> begin now would do the same output.
We do use ASM but like I said when I issue the:
GGSCI> alter extract <source extract name> thread 1 extseqno <sequence # from v$log query>
It works like it should.
Very weird.
- JasonYes, supplemental logging is enabled on both the source and the targets, but why would supplemental logging on the targets have any affect on why the Source Extract on the source can't read from the source redo log?
This is not a RAC database, rather single-instance with one thread. Also, we are using DBLOGREADER functionality as it is an 11.2.0.3 database.
My issue is simply, when I start the source extract from being down, meaning it isn't running, I issue this command:
alter <source extract> begin now
start <source extract>
view report <source extract>
OGG-01515 Positioning to begin time <today's date and time> ie Mar 4, 2013, 3:26:39 PM. (this is repeated over and over and over)
If I perform a
info <source extract> detail---> I see the following:
Log Read Checkpoint Oracle Redo Logs 2013-03-04 15:26:39 Thread 1, Seqno 0, RBA 0 (why is it showing 0, becuase it can't read the redo, WHY NOT?)
Extract Source BEGIN END
Not Available <today's date> <today's date> (repeat....)
However, if I retreive the Redo Log number and I issue:
alter spe thread 1 extseqno (redo log sequence #)
start spe.
Then it works okay. I have to manually tell it what redo log to begin reading from. Why?
- Jason
Edited by: 924317 on Mar 4, 2013 9:03 AM -
When occurs crash recovery,why use active online redo log not archived log?
If current redo log had archived, but it's still 'ACTIVE'. As we all know, archived log is just an archived copy of the current redo log which is still 'ACTIVE', they have the same data. But why use active online redo log not archived log for crash recovery?(I think, if crash recovery can use archived log, then whether the online redo log is 'ACTIVE' or not, it can be overwritten)
Quote:
Re: v$log : How redo log file can have a status ACTIVE and be already archived?
Hemant K Chitale
If your instance crashes, Oracle attempts Instance Recovery -- reading from the Online Redo Logs. It doesn't need ArchiveLogs for Instance Recovery.
TanelPoder
Whether the log is already archived or not doesn't matter here, when the instance crashes, Oracle needs some blocks from that redolog. Archivelog is just an archived copy of the redolog, so you could use either the online or achive log for the recovery, it's the same data in there (Oracle reads the log/archivelog file header when it tries to use it for recovery and validates whether it contains the changes (RBA range) in it what it needs).Aman.... wrote:
John,
Are you sure that the instance recovery (not the media recovery) would be using the archived redo logs? Since the only thing that would be lost is the isntance, there wouldn't be any archived redo log generated from the Current redo log and the previous archived redo logs, would be already checkpointed to the data file, IMHO archived redo logs won't participate in the instance recovery process. Yep, shall watch the video but tomorrow .
Regards
Aman....
That's what I said. Or meant to say. If Oracle used archivelogs for instance recovery, it would not be possible to recover in noarchive log mode. So recovery relies exclusively on the online log.
Sorry I wasted your time, I'll try to be less ambiguous in future -
How to find the configuration status of REDO logs files?
I am in the process of moving the redo log files.
Before that I want to find out whether it is set up as duplex or any other configurations.
How to find the REDO log configurations.
Oracle 10g R2
Thank you,
SmithExample:
Not duplexed redo log - if number of member is 1, then it is not duplexed:
SQL> select group#, members from v$log;
GROUP# MEMBERS
1 1
2 1
3 1
SQL> select group#, member from v$logfile;
GROUP# MEMBER
1 /u01/app/oracle/oradata/db1/redo01.log
2 /u01/app/oracle/oradata/db1/redo02.log
3 /u01/app/oracle/oradata/db1/redo03.log
SQL> alter database add logfile member '/u01/app/oracle/oradata/db1/redo01_2.log' to group 1;
Database altered.
SQL> alter database add logfile member '/u01/app/oracle/oradata/db1/redo02_2.log' to group 2;
Database altered.
SQL> alter database add logfile member '/u01/app/oracle/oradata/db1/redo03_2.log' to group 3;
Database altered.Duplexed redolog
SQL> select group#, members from v$log;
GROUP# MEMBERS
1 2
2 2
3 2
SQL> select group#, member from v$logfile;
GROUP# MEMBER
1 /u01/app/oracle/oradata/db1/redo01.log
2 /u01/app/oracle/oradata/db1/redo02.log
3 /u01/app/oracle/oradata/db1/redo03.log
1 /u01/app/oracle/oradata/db1/redo01_2.log
2 /u01/app/oracle/oradata/db1/redo02_2.log
3 /u01/app/oracle/oradata/db1/redo03_2.log
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