Reading Orcle current online redo logs

Hi,
We are able to read the SQL Server Transactional Log. We are trying to do that in case Oracle. Can anyone put some light on this?
Is there any third party tools doing this? Is this a feasible idea or not.
Regards,
Kalyan

You can use Logminer to look into the archived redo logs.
Why do you want to look at this though?

Similar Messages

Commit Completes although current online redo log file have been removed.

Although i have removed current online redo log file in linux os (Oracle Linux),when i type "commit" it says that "commit complete".
Is this fair for this princip?*:" if Only when all redo records associated with a given transaction are safely on disk in the online logs is the user process notified that the transaction has been committed."*
I think that it can lead to loss of data in some cases..I'm using Oracle 11g R2 on OEL (x64)..
Can anyone explain me ? I'm getting stuck in this situation..
P.S : I haven't multiplexed current ORL group files...

Javid wrote:
Although i have removed current online redo log file in linux os (Oracle Linux),when i type "commit" it says that "commit complete".
Is this fair for this princip?*:" if Only when all redo records associated with a given transaction are safely on disk in the online logs is the user process notified that the transaction has been committed."*
I think that it can lead to loss of data in some cases..I'm using Oracle 11g R2 on OEL (x64)..
Can anyone explain me ? I'm getting stuck in this situation..
In *nix, a file that is open by a process isn't really deleted until the process that has it completes. So even though you 'deleted' a redo log, oracle is still holding it. As soon as you stop your database (maybe even as soon as the db does a log switch) the redo will really be gone and no longer available. consider the implications for archive logging.
P.S : I haven't multiplexed current ORL group files...You need to fix that. the online logs are the achilles heel of the database. That's why it is standard practice to multiplex them.

The file structure online redo log, archived redo log and standby redo log

I have read some Oracle documentation for file structure and settings in Data Guard environment. But I still have some doubts. What is the best file structure or settings in Oracle 10.2.0.4 on UNIX for a data guard environment with 4 primary databases and 4 physical standby databases. Based on Oracle documents, there are 3 redo logs. They are: online redo logs, archived redo logs and standby redo logs. The basic settings are:
1. Online redo logs --- This redo log must be on Primary database and logical standby database. But it is not necessary to be on physical standby database because physical standby is not open. It doesn't generate redo log. However, if don't set up online redo log on physical standby, when primary failover and switch standby as primary. How can standby perform without online redo logs? In my standby databases, online redo logs have been set up.
2. Archived redo logs --- It is obviously that primary database, logical and physical standby database all need to have this log file being set up. Primary use it to archive log files and ship to standby. Standby use it to receive data from archived log and apply to database.
3. Standby redo logs --- In the document, it says A standby redo log is similar to an online redo log, except that a standby redo log is used to store redo data received from another database. A standby redo log is required if you want to implement: The maximum protection and maximum availability levels of data protection and Real-time apply as well as Cascaded destinations. So it seems that this standby redo log only should be set up on standby database, not on primary database. Am my understanding correct? Because I review current redo log settings on my environment, I have found that Standby redo log directory and files have been set up on both primary and standby databases. I would like to get more information and education from experts. What is the best setting or structure on primary and standby database?

FZheng:
Thanks for your input. It is clear that we need 3 type of redo logs on both databases. You answer my question.
But I have another one. In oracle ducument, it says If you have configured a standby redo log on one or more standby databases in the configuration, ensure the size of the current standby redo log file on each standby database exactly matches the size of the current online redo log file on the primary database. It says: At log switch time, if there are no available standby redo log files that match the size of the new current online redo log file on the primary database. The primary database will shut down
My current one data gurard envirnment setting is: On primary DB, online redo log group size is 512M and standby redo log group size is 500M. On the standby DB, online redo log group size is 500M and standby redo log group size is 750M.
This was setup by someone I don't know. Is this setting OK? or I should change Standby Redo Log on standby DB to 512M to exactly meatch with redo log size on primary?
Edited by: 853153 on Jun 22, 2011 9:42 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

Open database if an active online redo log is missing

Hi,
Sorry for the rather long post, but I specified all the steps I performed and couldn't make it shorter :-(
I need an advice on how to open the database if an active online redo log is missing.
For test purposes I intentionally performed a shutdown abort when the redo log group 1 was in active state and then renamed its only member (REDO01.LOG) so that the database couldn't perform crash recovery using it. Then upon startup I obviously got the message:
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: 'H:\ORADATA\TESTDB\REDO01.LOG'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) The system cannot find the file specified.Ok, so I checked the state of the logs:
{noformat}
SQL>SELECT a.GROUP#, first_change#, SEQUENCE#, a.status, SUBSTR(b.MEMBER, 1, 40) MEMBER, b.status mem_status, a.archived
2    FROM v$log a, v$logfile b
3   WHERE a.GROUP# = b.GROUP#
4 ORDER BY a.GROUP#, b.MEMBER;
GROUP# FIRST_CHANGE# SEQUENCE# STATUS           MEMBER                         MEM_STA ARC
     1        592134         29 ACTIVE           H:\ORADATA\TESTDB\REDO01.LOG           YES
     2        592268         30 CURRENT          C:\ORADATA\TESTDB\REDO02.LOG           NO
     3        592129         28 ACTIVE           C:\ORADATA\TESTDB\REDO03.LOG           YES
{noformat}Since opening the database to perform a log switch and thus change the status of the redo log group 1 from ACTIVE to INACTIVE to recreate the member isn't possible, I performed database recovery.
SQL>recover database until cancel;
ORA-00279: change 592129 generated at 02/04/2009 10:31:15 needed for thread 1
ORA-00289: suggestion : C:\ORACLE\PRODUCT\10.2.0\FLASH_RECOVERY_AREA\TESTDB\ARCHIVELOG\2009_02_04\O1_MF_1_28_%U_.ARC
ORA-00280: change 592129 for thread 1 is in sequence #28
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
ORA-00279: change 592134 generated at 02/04/2009 10:31:28 needed for thread 1
ORA-00289: suggestion : C:\ORACLE\PRODUCT\10.2.0\FLASH_RECOVERY_AREA\TESTDB\ARCHIVELOG\2009_02_04\O1_MF_1_29_%U_.ARC
ORA-00280: change 592134 for thread 1 is in sequence #29
ORA-00278: log file 'C:\ORACLE\PRODUCT\10.2.0\FLASH_RECOVERY_AREA\TESTDB\ARCHIVELOG\2009_02_04\O1_MF_1_28_4RLR3JS9_.ARC' no longer needed for this rec
overy
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
'C:\ORACLE\PRODUCT\10.2.0\FLASH_RECOVERY_AREA\TESTDB\ARCHIVELOG\2009_02_04\O1_MF_1_29_4RLR4MF3_.ARC'
ORA-00279: change 592268 generated at 02/04/2009 10:32:03 needed for thread 1
ORA-00289: suggestion : C:\ORACLE\PRODUCT\10.2.0\FLASH_RECOVERY_AREA\TESTDB\ARCHIVELOG\2009_02_04\O1_MF_1_30_%U_.ARC
ORA-00280: change 592268 for thread 1 is in sequence #30
ORA-00278: log file 'C:\ORACLE\PRODUCT\10.2.0\FLASH_RECOVERY_AREA\TESTDB\ARCHIVELOG\2009_02_04\O1_MF_1_29_4RLR4MF3_.ARC' no longer needed for this rec
overy
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
'C:\ORADATA\TESTDB\REDO02.LOG'
Log applied.
Media recovery complete.
SQL>So for log sequence #28 I accepted the proposed archived redo log in the FRA, for sequence #29 (that's the online redo log that is missing!) I manually specified its archived copy, and for sequence #30 I specified the CURRENT online redo log. And as it seems the media recovery was successful.
Next I tried to open the database but again got the error:
SQL>alter database open noresetlogs;
alter database open noresetlogs
ERROR at line 1:
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: 'H:\ORADATA\TESTDB\REDO01.LOG'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) The system cannot find the file specified.
The status of the log groups and its members is exactly as it was in the first query I wrote above, i.e. the redo log group 1 is still ACTIVE, so it's needed for crash recovery (which I had already done manually if I understand correctly how Oracle works!). I also checked if the datafiles are inconsistent (described in metalink doc id 1015544.102):
SQL>SELECT DISTINCT CHECKPOINT_CHANGE#, FUZZY FROM V$DATAFILE_HEADER;
CHECKPOINT_CHANGE# FUZ
            592269 NOSo, everything seems ok as far as datafile consistency is concerned.
My question is: how can I rename/drop/clear/whatever the member of redo log group 1 to open the database?
I tried to rename the log file member, to add another member to it, to open the database with resetlogs, to clear the logfile group 1, but all without success:
1)
SQL>alter database clear logfile group 1;
alter database clear logfile group 1
ERROR at line 1:
ORA-01624: log 1 needed for crash recovery of instance testdb (thread 1)
ORA-00312: online log 1 thread 1: 'H:\ORADATA\TESTDB\REDO01.LOG'
2)
SQL>alter database open resetlogs;
alter database open resetlogs
ERROR at line 1:
ORA-01139: RESETLOGS option only valid after an incomplete database recovery
3)
SQL>alter database rename file 'H:\ORADATA\TESTDB\REDO01.LOG' to 'C:\ORADATA\TESTDB\REDO01.LOG';
alter database rename file 'H:\ORADATA\TESTDB\REDO01.LOG' to 'C:\ORADATA\TESTDB\REDO01.LOG'
ERROR at line 1:
ORA-01511: error in renaming log/data files
ORA-01512: error renaming log file H:\ORADATA\TESTDB\REDO01.LOG - new file C:\ORADATA\TESTDB\REDO01.LOG not found
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) The system cannot find the file specified.
4)
SQL>alter database add logfile member 'C:\ORADATA\TESTDB\REDO01.LOG' to group 1;
alter database add logfile member 'C:\ORADATA\TESTDB\REDO01.LOG' to group 1
ERROR at line 1:
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: 'H:\ORADATA\TESTDB\REDO01.LOG'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) The system cannot find the file specified.Sorry again for the long post and thank you in advance for any suggestion.
Regards,
Jure

You could check if the recovery was complete by (re)creating the controlfile with the resetlogs option.
<CREATE CONTROLFILE REUSE DATABASE define_db_name RESETLOGS NOARCHIVELOG
...>Thanks for the hint. If possible, could you only check if the steps I'm going to perform are ok.
I did an "alter database backup controlfile to trace;" and then extracted the create controlfile definition part. So in essence I should run the following statements:
CREATE CONTROLFILE REUSE DATABASE "TESTDB" RESETLOGS ARCHIVELOG
    MAXLOGFILES 16
    MAXLOGMEMBERS 3
    MAXDATAFILES 100
    MAXINSTANCES 8
    MAXLOGHISTORY 292
LOGFILE
GROUP 1 'C:\ORADATA\TESTDB\REDO01.LOG' SIZE 20M,
GROUP 2 'C:\ORADATA\TESTDB\REDO02.LOG' SIZE 20M,
GROUP 3 'C:\ORADATA\TESTDB\REDO03.LOG' SIZE 20M
-- STANDBY LOGFILE
DATAFILE
'C:\ORACLE\PRODUCT\10.2.0\ORADATA\TESTDB\SYSTEM01.DBF',
'C:\ORACLE\PRODUCT\10.2.0\ORADATA\TESTDB\UNDOTBS01.DBF',
'C:\ORACLE\PRODUCT\10.2.0\ORADATA\TESTDB\SYSAUX01.DBF',
'C:\ORACLE\PRODUCT\10.2.0\ORADATA\TESTDB\USERS01.DBF'
CHARACTER SET EE8MSWIN1250
ALTER DATABASE OPEN RESETLOGS;
ALTER TABLESPACE TEMP ADD TEMPFILE 'C:\ORACLE\PRODUCT\10.2.0\ORADATA\TESTDB\TEMP01.DBF' REUSE;Is that correct?
About the RMAN backups: Wouldn't a 'CATALOG RECOVERY AREA' populate the controlfile with backup information again (I'm not using a recovery catalog in this case)?
Thanks for the help!
Regards,
Jure

Abot loss online Redo log group

Hi,
Is there different from recovering between loss CURRENT online redo log group and ACTIVE online redo log group?
Both of them are needed to incomplete recovery, right?

For CURRENT redolog recovery:
startup mount
recover database until cancel;
alter database open resetlogs;
For ACTIVE redolog recovery:
If the database is still running, force a checkpoint by issuing the following command:
alter system checkpoint;
If above was successful and if the lost group has been archived then issue:
alter database clear logfile group <number of the online redo log group>;
And if the lost group has NOT been archived then issue:
alter database clear logfile unarchived group <number of the online redo log group>;
alter database open;
If the database is not running (crashed) then
startup mount
recover database until cancel;
alter database open resetlogs;
Daljit Singh

Multiplexing Online redo logs, archive logs, and control files.

Currently I am only multiplexing my control files and online redo logs, My archive logs are only going to the FRA and then being backed up to tape.
We have to replace disks that hold the FRA data. HP says there is a chance we will have to rebuild the FRA.
As my archive logs are going to the FRA now, can I multiplex them to another disk group? And if all of the control files, online redo logs and archive logs are multiplexed to another disk group, when ASM dismounts the FRA disk group due to insufficient number of disks, will the database remain open and on line.
If so then I will just need to rebuild the ASM volumes, and the FRA disk group and bring it to the mount state, correct?
Thanks!

You can save your online redo logs and archive logs anywhere you want by making use of of init params create_online_log_dest and log_archive_dest_n. You will have to create new redo log groups in the new location and drop the ones in the FRA. The archive logs will simply land wherever you designate with log_archive_dest_n parameters. Moving the control files off FRA is a little trickier because you will need to restore your controlfile to a non-FRA destination and then shutdown your instance, edit the control file param to reflect changes and restart.
I think you will be happier if you move everything off the FRA diskgroup before dismounting it, and not expecting the db to automagically recover from the loss of files on the FRA.

Recover when Online Redo Log lost.

Hi,all.
How do I recover the db while all the online redo log files were lost.
The database is running in archive mode and all the archived redo log files were saved well.
But since last hot backup,I have done some table inserting with nologging.
Now the database can not be opened.
Who can tell me how to recover the db to the recent state.
I remember the db was shutdown immediate.
(Do it make any difference to online redo log file between shutdown immediate and abort?)
Thanks.
wy.

I find out if I shutdown immediate and remove all the redo log files,I can recover the database as below:
SQL> startup
ORACLE instance started.
Total System Global Area 109164572 bytes
Fixed Size 75804 bytes
Variable Size 59498496 bytes
Database Buffers 49512448 bytes
Redo Buffers 77824 bytes
Database mounted.
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: 'D:\ORACLE\ORADATA\ORCL\REDO03.LOG'
SQL> recover database until cancel
Media recovery complete.
SQL> alter database open resetlogs;
Database altered.
but if I shutdown abort,I can not recover the database.
SQL> startup
ORACLE instance started.
Total System Global Area 109164572 bytes
Fixed Size 75804 bytes
Variable Size 59498496 bytes
Database Buffers 49512448 bytes
Redo Buffers 77824 bytes
Database mounted.
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: 'D:\ORACLE\ORADATA\ORCL\REDO03.LOG'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) O5M3UR2;5=V86(5DND<~!#
SQL> recover database until cancel
ORA-00279: change 690879 generated at 08/09/2004 16:34:04 needed for thread 1
ORA-00289: suggestion : D:\ORACLE\ORADATA\ORCL\ARCHIVE\ORCLT001S00002.ARC
ORA-00280: change 690879 for thread 1 is in sequence #2
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
auto
ORA-00279: change 690963 generated at 08/09/2004 16:34:08 needed for thread 1
ORA-00289: suggestion : D:\ORACLE\ORADATA\ORCL\ARCHIVE\ORCLT001S00003.ARC
ORA-00280: change 690963 for thread 1 is in sequence #3
ORA-00278: log file 'D:\ORACLE\ORADATA\ORCL\ARCHIVE\ORCLT001S00002.ARC' no
longer needed for this recovery
ORA-00308: cannot open archived log
'D:\ORACLE\ORADATA\ORCL\ARCHIVE\ORCLT001S00003.ARC'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) O5M3UR2;5=V86(5DND<~!#
ORA-01547: warning: RECOVER succeeded but OPEN RESETLOGS would get error below
ORA-01194: file 1 needs more recovery to be consistent
ORA-01110: data file 1: 'D:\ORACLE\ORADATA\ORCL\SYSTEM01.DBF'
SQL> recover database until cancel
ORA-00279: change 690963 generated at 08/09/2004 16:34:08 needed for thread 1
ORA-00289: suggestion : D:\ORACLE\ORADATA\ORCL\ARCHIVE\ORCLT001S00003.ARC
ORA-00280: change 690963 for thread 1 is in sequence #3
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
CANCEL
ORA-01547: warning: RECOVER succeeded but OPEN RESETLOGS would get error below
ORA-01194: file 1 needs more recovery to be consistent
ORA-01110: data file 1: 'D:\ORACLE\ORADATA\ORCL\SYSTEM01.DBF'
ORA-01112: media recovery not started
SQL> ALTER DATABASE OPEN RESETLOGS;
ALTER DATABASE OPEN RESETLOGS
ERROR at line 1:
ORA-01194: file 1 needs more recovery to be consistent
ORA-01110: data file 1: 'D:\ORACLE\ORADATA\ORCL\SYSTEM01.DBF'
So How to recover the database when the db shutdown abort and all the online redo log were lost?

Purpose of ONLINE REDO LOG FILES - Media or Instance recovery or BOTH ?

Hi
Currently studying this topic for the 1z0-031 exam and am a little confused.
my books (from instructor led class) say
-redo logs are a mean to provide redo transactions in the event of a DATABASE recovery
-redo log buffer gets flushed to redo log files to provide a recovery mechanism in case of MEDIA FAILURE
Then it says
-Online redo log files are used in a situation such as an INSTANCE FAILURE to recover uncommitted data which has not yet been written to the data files
- online redo log files are used for RECOVERY only.
Am i misunderstanding? Or are redo log files for both MEDIA and INSTANCE recovery? Or just INSTANCE ?
confused....
Amanjit

Online Redo Log Files are used in a sense for both Media and Instance Recovery. If your database is in NoArchive Mode then you will only be able to use the Redo Log Files for instance recover. But if you are running in Archive Log Mode then Redo Log Files are archived and will allow you to recover from media failure.

RMAN x Online redo logs - doubt

When using RMAN's online hot backup, RMAN does not back up the online redo logs, does it?
Is there a way to do that?

The online redo logs files are never backed up by RMAN or any hot backup method.
The online redo logs files contain the latest data or redo generated by the database.(The data comes from redo log buffer written by LGWR).
The contents of the current redo logs are not archived until a log switch occurs.
This means if all your members in a redo log group fails, you would lose the latest information. So its best practice to invoke log switch before starting archivelog backup.

Best practice - online redo logs and virtualization

I have a 10.1.0.4 instance (soon to be migrated to 11gr2) running under Windows Server 2003.
We use a non-standard disk distribution scheme -
on the c: drive we have oracle_home as well as directories for control files and online redo logs.
on the d: drive we have datafiles
on the e: drive we have archive log files and another directory with online redo logs and another copy of control file
my question is this:
is it smart practice to have ANY online redo logs or control file on the same spindle with archive logs?
Our setup works fairly well but we are in the process of migrating the instance first to ESX server and SAN and then secondly to 11gtr2 64bit under server 2008 64 and when we bring up our instance on the VM for testing we find that benchmarking the ESX server (dual Xeon 3.4ghz with 48gb RAM running against FalconStor NSS SAN with 15k SAS disks over iSCSI) against the production physical server (dual Xeon 2.0ghz with 4gb RAM using direct attached SATA 7200rpm drives) we find that some processes run faster on the ESX box and some run 40-100% slower. Running Statspack seems to identify lots of physical read waits as well as some waits for redo and controlfiles.
Is it possible that in addition to any overhead introduced by ESX and iSCSI (we are running Jumbo Frames over 1gb) we may have contention because the archive logs are on the same "spindle" (virtual) as the online redo and control files?
We're looking at multiple avenues to bring the 2 servers in line from a performance standpoint - db configuration, memory allocation, possible move to 10gb network, possible move to SSD storage tray, possible application rewrites. But from the simplest low hanging fruit idea, if these files should not be on the same spindle thats an easy change to make and possibly eke out an improvement.
Ideas?
Mike

Hi,
"Old" Oracle standard is to use as many spindles as possible.
It looks to me, you have only 1 disk with several partitions on it ??
In my honest opinion you should anyway start by physically seperating OS from Oracle, so let the C: drive to the Windows OS
Take another physical seperate D: drive to install you application.
Use yet another set of physical drives, preferably in RAID10 setup, for your database and redo logs
And finally yet another disk for the archive logs.
We have recently configured a Windows 2008 server with an 11G Db, which pretty much follows the above setup.
All non RAID10 disks are RAID1 ( mirror ) and we even have some SSD's for hot tables and redo-logs.
The machine, or must I say the database, operates like a high speed train, very, very fast.
Ofcourse keep in mind the number of cores ( not only for licensing ) and the amount of memory.
Try to prevent the system from swapping, because that is a performance killer!
Edit: And even if you put a virtual layer in between, try to seperate the virtual disks as much as possible over physical disks
Success!
FJFranken
Edited by: fjfranken on 7-okt-2011 7:19

Can we use online redo log to recover lost datafile in NOARCHIVE mode?

I am working on OCA exam and confued about these 2 sample questions. (similar questions with totally different answer)
Please give me hint about the different between these 2 questions.
** If the database is in NOARCHIVELOG mode, and one of the datafile for tablespace USERS is lost, what kind of recovery is possible? (answer: B)
A. All transactions except those in the USERS tablespace are recoverable up to the loss of the datafile.
B. Recovery is possible only up to the point in time of the last full database backup.
C. The USERS tablespace is recoverable from the online redo log file as long as none of the redo log files have been reused since the last backup.
D. Tablespace point in time recovery is available as long as a full backup of the USERS tablespace exists.
** The database of your company is running in the NOARCHIVELOG mode. You perform a complete backup of the database every night. On Monday morning, you lose the USER1.dbf file belonging to the USERS tablespace. Your database has four redo log groups, and there have been two log switches since Sunday night's backup.
Which is true (answer: B)
A. The database cannot be recovered.
B. The database can be recovered up to the last commit.
C. The database can be recovered only up to the last completed backup.
D. The database can be recovered by performing an incomplete recovery.
E. The database can be recovered by restoring only the USER!.dbf datafile from the most recent backup.

I think Gaurav is correct, you can recover to the last commit even in NOARCHIVELOG, as long as all the changes in the redo logs have not been overwritten. So answer should be B for question 2.
Here is my test:
SQL> select log_mode from v$database;
LOG_MODE
NOARCHIVELOG
SQL> select tablespace_name, file_name from dba_data_files;
TABLESPACE_NAME
FILE_NAME
USERS
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\USERS01.DBF
SYSAUX
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\SYSAUX01.DBF
UNDOTBS1
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\UNDOTBS01.DBF
SYSTEM
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\SYSTEM01.DBF
DATA
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\DATA01.DBF
SQL> create table names
2 ( name varchar(16))
3 tablespace users;
Table created.
so this segment 'names' is created in the datafile users01.
At this point I shut down and mount the DB, then:
RMAN> backup database;
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:29
Finished backup at 06-OCT-07
SQL>alter database open
SQL> insert into names values ('pippo');
1 row created.
SQL> commit;
Commit complete.
SQL>shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
At this point I delete datafile users01 and restart:
SQL> startup
ORACLE instance started.
Total System Global Area 167772160 bytes
Fixed Size 1247900 bytes
Variable Size 67110244 bytes
Database Buffers 96468992 bytes
Redo Buffers 2945024 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 4 - see DBWR trace file
ORA-01110: data file 4: 'C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\USERS01.DBF'
restoring the backup taken before inserting the value 'pippo' in table names:
RMAN> restore database;
Starting restore at 06-OCT-07
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile backupset restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
restoring datafile 00001 to C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\SYSTEM01.D
BF
restoring datafile 00002 to C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\UNDOTBS01.
DBF
restoring datafile 00003 to C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\SYSAUX01.D
BF
restoring datafile 00004 to C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\USERS01.DB
F
restoring datafile 00005 to C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORA101RC\DATA01.DBF
channel ORA_DISK_1: reading from backup piece C:\ORACLE\PRODUCT\10.2.0\DB_1\DATA
BASE\0AITR52K_1_1
channel ORA_DISK_1: restored backup piece 1
piece handle=C:\ORACLE\PRODUCT\10.2.0\DB_1\DATABASE\0AITR52K_1_1 tag=TAG20071006
T181337
channel ORA_DISK_1: restore complete, elapsed time: 00:02:07
Finished restore at 06-OCT-07
RMAN> recover database;
Starting recover at 06-OCT-07
using channel ORA_DISK_1
starting media recovery
media recovery complete, elapsed time: 00:00:05
Finished recover at 06-OCT-07
SQL> alter database open;
Database altered.
SQL> select * from names;
NAME
pippo
SQL>
enrico

Online redo log files being removed physically

Grid Infra version: 11.2.0.4
RDBMS Version: 11.2.0.4
Although this is a RAC DB, this is not a RAC-specific question. Hence posting it here.
Few months back, I remember issuing a command similair to below (DROP LOGFILE GROUP ...) and the redo log files were still physically present in the diskgroup.
If I remember correctly, the file is not deleted physical so that we can use the REUSE functionality (ALTER DATABASE ADD LOGFILE MEMBER '+REDO/orcl/onlinelog/redo1b.log' reuse to group 11; ) ie. you can use the REUSE command to add the logfile of the same name which is physically present in OS Filesystem/Diksgroup to redo log group.
But today, after I issued the below command, I checked the diskgroup location from ASMCMD
SQL> alter database drop logfile group 31;
Database altered.
From ASMCMD, I can that the file has disappeared physically. Is this a new feature with 11.2.0.4 or am I missing something here ?
ASMCMD> ls +DATA/msblprd/onlinelog/group_31.548.833154995
ASMCMD-8002: entry 'group_31.548.833154995' does not exist in directory '+DATA/msblprd/onlinelog/'

Just to add to what Aman has said.
It is a bad practice not to let OMF decide the placement of Online redo logs because of this issue especially when you use ASM.
Executing rm command in Linux/Unix is easy but Dropping ASM aliases in the disk group can be a hassle.
This is documented.
"When a redo log member is dropped from the database, the operating system file is not deleted from disk. Rather, the control files of the associated database are updated to drop the member from the database structure. After dropping a redo log file, ensure that the drop completed successfully, and then use the appropriate operating system command to delete the dropped redo log file."
http://docs.oracle.com/cd/E11882_01/server.112/e25494/onlineredo.htm#ADMIN11324
BTW . You don't even need to set db_create_online_log_dest_n to enable OMF for ORLs.
SQL> show parameter log_dest
NAME                                 TYPE        VALUE
db_create_online_log_dest_1          string
db_create_online_log_dest_2          string
db_create_online_log_dest_3          string
db_create_online_log_dest_4          string
db_create_online_log_dest_5          string
SQL> show parameter db_create_file_dest
NAME                                 TYPE        VALUE
db_create_file_dest                  string      +MBL_DATA
alter database add logfile thread 4
group 31 ('+MBL_DATA','+MBL_FRA') size 4096M,
group 32 ('+MBL_DATA','+MBL_FRA') size 4096M,
group 33 ('+MBL_DATA','+MBL_FRA') size 4096M,
group 34 ('+MBL_DATA','+MBL_FRA') size 4096M ;
Database altered.
And redo logs will be neatly placed as shown below
   INST     GROUP# MEMBER                                             STATUS           ARC
         4         31 +MBL_DATA/bsblprd/onlinelog/group_31.276.832605441 UNUSED           YES
                      +MBL_FRA/bsblprd/onlinelog/group_31.297.832605445 UNUSED           YES
                   32 +MBL_DATA/bsblprd/onlinelog/group_32.547.832605451 UNUSED           YES
                      +MBL_FRA/bsblprd/onlinelog/group_32.372.832605457 UNUSED           YES
                   33 +MBL_DATA/bsblprd/onlinelog/group_33.548.832605463 UNUSED           YES
                      +MBL_FRA/bsblprd/onlinelog/group_33.284.832605469 UNUSED           YES
                   34 +MBL_DATA/bsblprd/onlinelog/group_34.549.832605475 UNUSED           YES
                      +MBL_FRA/bsblprd/onlinelog/group_34.359.832605481 UNUSED           YES

Physical Standby Online Redo log files,

Hi,
I'm trying to create a physical standby database (10.2.0.3). I'm a little confused about the requirement for online redo logs on the standby.
in my standby alert log I get the following when I issue:
SQL> alter database recover managed standby database disconnect from session
"ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: '/appl/oradata/prod/prod_1_redo_01_02.log'
ORA-27037: unable to obtain file status
SVR4 Error: 2: No such file or directory
Additional information: 3"
/appl/oradata/prod/prod_1_redo_01_02.log is the path to the location of the online redo logs on the production system. This file does not exist on the standby filesystem so the error is correct.
I assume that it gets this information from the standby control file I created on the production system and copied over to the standby.
Do I need to copy the online redo logs from the primary over to the standby site or do I need to create online redo logs on the standby?
Does the standby need to have redo log files?
I'm not talking about 'standby log files' of the type created using 'alter database add standby log file'. I've not got that far yet.
I just need to establish if a physical standby requires online redo log files?
Thanks in advance,
user234564

I wanted to update this thread since I've been dealing with the exact same errors. The basic question is: "does a physical standby need the online redo logs?"
Answer: Not really, until one wants to switchover or failover (and become a primary database). Furthermore, whenever the MRP process is started, Oracle prepares for a possible switchover/failover by "clearing" the online redo logs (MetaLink note# 352879.1). It is not a big deal, since Oracle will build the actual redo files when the "alter database open resetlogs" is accomplished during a "role transition."
In our situation, we have decided to use our standby for nightly exports. We stop MRP, open the database read-only, then restart MRP. We built these standby DBs with RMAN. The RMAN duplicate process will not build the online redo log files until the database is opened for read/write (with resetlogs). However, we haven't had a need for read/write (i.e. a switchover).
Thus, every morning we have been getting the same errors that "user234564" posted above. At first the errors seemed scary, then we realized they were just a nusiance. In order to clean things up, all I did was just "cp" our stanby redo logs (SRL) into our online redo directories ensuring the names matched what was in v$logfile. When I restarted MRP, the alert log clearly showed Oracle clearing these "newly found" online redo logs.

Problem with Whole Database Online+Redo log Backup

Dear Marcus Sir,
I am facing while taking "Whole Database Online+Redo log Backup" through DB13 T-Code.
Below is the "Problem part of the Backup log", however if you need I will send you full log.
Hope you will find out problem soon
#FILE..... /oracle/ANP/sapdata2/sr3_8/sr3.data8
#SAVED.... sr3.data8 ANPB260810/12
BR0280I BRBACKUP time stamp: 2010-08-27 11.03.22
BR0063I 9 of 51 files processed - 19400.070 MB of 135986.469 MB done
BR0204I Percentage done: 14.27%, estimated end time: 11:47
BR0001I *******___________________________________________
BR0202I Saving /oracle/ANP/sapdata2/sr3_9/sr3.data9
BR0203I to /dev/rmt0.1 ...
BR0278E Command output of 'LANG=C dd obs=1024K bs=1024K if=/oracle/ANP/sapdata2/sr3_9/sr3.data9 of=/dev/rmt0.1':
dd read error: I/O error
462+0 records in
462+0 records out
BR0280I BRBACKUP time stamp: 2010-08-27 11.03.36
BR0279E Return code from 'LANG=C dd obs=1024K bs=1024K if=/oracle/ANP/sapdata2/sr3_9/sr3.data9 of=/dev/rmt0.1': 2
BR0222E Copying /oracle/ANP/sapdata2/sr3_9/sr3.data9 to/from /dev/rmt0.1 failed due to previous errors
BR0280I BRBACKUP time stamp: 2010-08-27 11.03.41
BR0317I 'Alter tablespace PSAPSR3 end backup' successful
BR0056I End of database backup: bedziydp.ant 2010-08-27 11.03.36
BR0280I BRBACKUP time stamp: 2010-08-27 11.03.41
BR0054I BRBACKUP terminated with errors
Warm Regards
Ahsan

Hi,
since you are getting a read error, it might as well be, that your datafile is defective.
Try the same dd-command to /dev/null, to see if it is possible to read the entire file.
First make sure that your null-device is existing, otherwise you might face a root-fs full problem.
dd obs=1024K bs=1024K if=/oracle/ANP/sapdata2/sr3_9/sr3.data9 of=/dev/null
or try a dbverify on it, which would also read the entire file and do a checksum test.
brbackup -c -u / -m /oracle/ANP/sapdata2/sr3_9/sr3.data9 -t online -w only_dbv
Good luck
Volker

Reading Orcle current online redo logs

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