Online redo logs in Flash Recovery Area

Hi,
Currently I have redo logs multiplexed on two separate disks. I want to add a new member to each log file group that goes in flash recovery area. What is the easiest way to accomplish this?
It seems to me that I can only do this by dropping the existing groups and recreating them. If I decide to go this route, what parameters do I need to set so that 3 members are created for each group?
Thanks

Simply issue 'alter database add logfile group <n>;', don't specify a location. Assuming 'db_recovery_file_dest' is correctly set this will create an Oracle managed file under <FRA>/onlinelog/<OMF-filename>, something like
4 ONLINE
C:\ORACLE\FLASH_RECOVERY_AREA\ORACLE\ONLINELOG\O1_MF_4_5WRBM1C4_.LOG
GROUP# STATUS TYPE
MEMBER
IS_
YES
Werner

Similar Messages

Redo logs and Flash recovery area

Hi,
Is it a good practice to place a copy of the (multiplexed) online redo at the flash recovery area? Wouldn't it be better to place a copy of the archived log at the flash recovery area?

user492400 wrote:
Hi,
Is it a good practice to place a copy of the (multiplexed) online redo at the flash recovery area? Wouldn't it be better to place a copy of the archived log at the flash recovery area?Its not only the archvielogs that should be placed in the FRA. FRA is supposed to contain one copy of the archive logs and the rest 9 destinations are given to you for the multiplexing of it. The idea of multiplexing the redo logs and placing them anywhere( not just on the FRA itself) is simply required so that you won't get to a situation where you would lose all the redo log files and thus have to recreate them, losing the data inside them. So aleast one copy of the log files should be there and where you want to put it, that would depend on you.
HTH
Aman....

Disk array configurations with oracle redo logs and flash recovery area.

Dear Oracle users,
We are planning to buy the new server for oracle database 10g standard edition. We put oracle database file, redo logs, and flash recovery area on each of disk array. My question is what is the best disk array configuration for redo logs and flash recovery area? RAID 10 or RAID 1? Is that possible we can duplicate Flash recovery area to the other location (such as net work drive) at the same time? Since we only have single disk array controller to connect to the disk arrays, I am try to avoid the single failure that will lose archive logs and daily backup.
thanks,
Belinda

Thank you so much for the suggestion. Could you please let me know the answer for my question of FRA redundancy?
“Is that possible we can duplicate Flash recovery area to the other location (such as net work drive) at the same time? Since we only have single disk array controller to connect to the disk arrays, I am try to avoid the single failure that will lose archive logs and daily backup.”

Changing the location of archive log from flash recovery area PLZ HELP!!!

Hi All,
My archive log is being stored in flash memory area which got full and the production server went down.
alert log file details.....
ORA-19809: limit exceeded for recovery files
ORA-19804: cannot reclaim 43432960 bytes disk space from 2147483648 limit
*** 2010-04-25 14:22:49.777 62692 kcrr.c
ARCH: Error 19809 Creating archive log file to
'/oracle/product/10.2.0/flash_rec
overy_area/EDWREP/archivelog/2010_04_25/o1_mf_1_232_%u_.arc'
*** 2010-04-25 14:22:49.777 60970 kcrr.c
kcrrfail: dest:10 err:19809 force:0 blast:1I removed the files and started the database,
Can someone kindly tell me as to how to avoid this problem in future by keeping archive log destination in flash recovery area.
I want to change the location of archive log files, can someone please guide me as to hiow to do that
I changed the size of flash recovery area for the time being, but i am afraid it will be full again!!
SQL> select * from v$flash_recovery_area_usage;
FILE_TYPE    PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES
CONTROLFILE                   0                         0               0
ONLINELOG                     0                         0               0
ARCHIVELOG                99.44                         0              57
BACKUPPIECE                   0                         0               0
IMAGECOPY                     0                         0               0
FLASHBACKLOG                  0                         0               0
6 rows selected.
SQL> alter system set DB_RECOVERY_FILE_DEST_SIZE = 4G ;
System altered.
SQL> select * from v$flash_recovery_area_usage;
FILE_TYPE    PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES
CONTROLFILE                   0                         0               0
ONLINELOG                     0                         0               0
ARCHIVELOG                49.72                         0              57
BACKUPPIECE                   0                         0               0
IMAGECOPY                     0                         0               0
FLASHBACKLOG                  0                         0               0
6 rows selected.regards,
Edited by: user10243788 on Apr 25, 2010 6:12 AM

user10243788 wrote:
Hi All,
My archive log is being stored in flash memory area which got full and the production server went down.
alert log file details.....
ORA-19809: limit exceeded for recovery files
ORA-19804: cannot reclaim 43432960 bytes disk space from 2147483648 limit
*** 2010-04-25 14:22:49.777 62692 kcrr.c
ARCH: Error 19809 Creating archive log file to
'/oracle/product/10.2.0/flash_rec
overy_area/EDWREP/archivelog/2010_04_25/o1_mf_1_232_%u_.arc'
*** 2010-04-25 14:22:49.777 60970 kcrr.c
kcrrfail: dest:10 err:19809 force:0 blast:1I removed the files and started the database,
Can someone kindly tell me as to how to avoid this problem in future by keeping archive log destination in flash recovery area.
I want to change the location of archive log files, can someone please guide me as to hiow to do that
I changed the size of flash recovery area for the time being, but i am afraid it will be full again!!
SQL> select * from v$flash_recovery_area_usage;
FILE_TYPE    PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES
CONTROLFILE                   0                         0               0
ONLINELOG                     0                         0               0
ARCHIVELOG                99.44                         0              57
BACKUPPIECE                   0                         0               0
IMAGECOPY                     0                         0               0
FLASHBACKLOG                  0                         0               0
6 rows selected.
SQL> alter system set DB_RECOVERY_FILE_DEST_SIZE = 4G ;
System altered.
SQL> select * from v$flash_recovery_area_usage;
FILE_TYPE    PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES
CONTROLFILE                   0                         0               0
ONLINELOG                     0                         0               0
ARCHIVELOG                49.72                         0              57
BACKUPPIECE                   0                         0               0
IMAGECOPY                     0                         0               0
FLASHBACKLOG                  0                         0               0
6 rows selected.regards,
Edited by: user10243788 on Apr 25, 2010 6:12 AMPointing the archive log dest (and/or the FRA) to a new location, or enlarging them, will do no good if you are not performing regular housekeeping on the archivelogs. You will just keep knocking down the same problem over and over.
If you simply delete the archivelogs at the OS level, the database will never know about it and it will continue to think the destination is full, based on records kept in the control file.
For regular housekeeping, you need to be doing something similar to this in rman:
run {
backup archivelog all not backed up 1 times tag='bkup_vlnxora1_arch';
delete noprompt archivelog all backed up 1 times to device type disk;
run {
delete noprompt obsolete;
crosscheck archivelog all;
delete noprompt expired archivelog all;

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

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.

Proper layout of datafiles, archivelogs, flash recovery area

Hi all,
Sorry a bit of a newb,
Have a question about how to layout my db files.
My understanding is that control and archivelog files should be multiplexed to a separate disk than the datafiles.
Is this also true for the flash_recovery_area?
Thanks for any help.

geeter wrote:
Hi all,
Sorry a bit of a newb,
Have a question about how to layout my db files.
My understanding is that control and archivelog files should be multiplexed to a separate disk than the datafiles.
Is this also true for the flash_recovery_area?
Thanks for any help.Lose your control file or your redo file, and you have a problem. Therefore, in a professional environment, the control file and redo logs need to be protected by multiplexing to different physical drives (not different partitions on same disk). One of those locations can be the same DASD as the database files.
Archivelogs should be bounced from online to nearline to offline storage. These days 'online' is inside flash recovery area. If you are paranoid, you can send archivelogs to multiple destinations (multiplex), although some form of disk protection (RAID 1 ... or 5 - ugh!) should be sufficient.
Flash Recovery Area can be inside ASM or on regular file system. If in ASM, consider using either RAID 1 under ASM and external failgroups, or normal failgroup mode to allow the system to do it's own RAID 1 equivalent. If on regular file system, use standard disk protection (RAID 1 or 5) to do the protection.
Oracle uses the SAME (Stripe and Mirror Everything) philosophy, so separating Fast Recovery Area (new name - used to be Flash Recovery Area in the ancient days of Oracle 10g) from database files is not needed.
Highly recommend you read the first chapter of the Database Concepts Manual and the first chapter of the Database Administrator Guide to get used to the docs, adn then use that as a pringboard (via table of contents) to the sections that answer your question. Start at http://tahiti.oracle.com to get to those docs - they are on the front page of the doc set for your favorite version.

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

Flash recovery area issue. I can not open the database??

Hi all
I am using oracle 11.2.0 .1.0 on windows
when i tried to start the database I got the following error.
ORA-03113: end-of-file on communication channel
I clear out all information in Trace file. I cleared out all operating system level audit trails. then i deleted archivelog files using operating system level delete. still my database is not opening???
I tried to start this using RMAN but got the same error. now i have deleted the files from flash recovery area how can i let oracle system to know that those are deleted and there is enough space. Rman does not execute crosschek commands at mount state of the database?
Need solution.
Regards
MAlik

malikdba wrote:
the last option which ask to delete the files. i already have deleted the files at operating system level. now the issue is how to let the system that the space is free in flash recovery area? rman is not running crosscheck command at mount stage of the target database. What steps should i follow now?
Thanks
malik
Are you saying you are getting an error while trying to crosscheck at mount? Or you simply don't believe it will work?
oracle:orcl$ rman target /
Recovery Manager: Release 11.2.0.2.0 - Production on Thu Jul 11 10:52:48 2013
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
connected to target database (not started)
RMAN> startup mount;
Oracle instance started
database mounted
Total System Global Area     839282688 bytes
Fixed Size                     2231128 bytes
Variable Size                503317672 bytes
Database Buffers             331350016 bytes
Redo Buffers                   2383872 bytes
RMAN> crosscheck archivelog all;
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=18 device type=DISK
specification does not match any archived log in the repository
RMAN>
A perfectly normal crosscheck at the mount stage

Online redo logs on a physical standby?

A question on REDO logs on physical standby databases. (10.2.0.4 db on Windows 32bit)
My PRIMARY has 3 ONLINE REDO groups, 2 members each, in ..ORADATA\LOCP10G
My PHYSICAL STANDBY has 4 STANDBY REDO groups, 2 members each, in ..ORADATA\SBY10G
I have shipping occurring from the primary in LGWR, ASYNC mode - max availablility
However I notice the STANDBY also has ONLINE REDO logs, same as the PRIMARY, in the ..ORADATA\SBY10G folder
According to the 10g Dataguard docs, section 2.5.1:
"Physical standby databases do not use an online redo log, because physical standby databases are not opened for read/write I/O."
I have tried to drop these on the STANDBY when not in apply mode, but I get the following:
SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;
Database altered.
SQL> ALTER DATABASE DROP LOGFILE GROUP 3;
ALTER DATABASE DROP LOGFILE GROUP 3
ERROR at line 1:
ORA-01275: Operation DROP LOGFILE is not allowed if standby file management is
automatic.
I also deleted them while the STANDBY instance was idle, but it recreated them when moved to MOUNT mode.
So my question is why is my PHYSICAL recreating and using these, if the docs say the shouldn't?
I saw the same error mentioned here: prob. with DataGuard
Is this a case of the STANDBY needing at least a notion of where the REDO logs will need to be should a failover occur, and if the files are already there, the standby database CONTROLFILE will hold onto them, as they are not doing any harm anyway?
Or, is this a prooduct of having management=AUTOMATIC - i.e. the database will create these 'automatically'
Ta
bt

According to the 10g Dataguard docs, section 2.5.1:
"Physical standby databases do not use an online redo log, because physical standby databases are not opened for read/write I/O."yes, those are used when database is open.
You should not perform any changes in Standby. Even if those exist online redo log files, whats the difficulty you have seen?
These will be used whenever you performed switchover/failover. So nothing to worry on this.
Is this a case of the STANDBY needing at least a notion of where the REDO logs will need to be should a failover occur, and if the files are already there, the standby database CONTROLFILE will hold onto them, as they are not doing any harm anyway?Then oracle functionality itself harm if you think in that way. When they not used in open then what the harm with that?
Standby_File_management --> for example if you add any datafile, those information will be in archives/redos once they applied on standby those will be added automatically when it is set to AUTO if its manual, then it creates a unnamed file in $ORACLE_HOME/dbs location later you have to rename that file and recovery need to perform .
check this http://docs.oracle.com/cd/B14117_01/server.101/b10755/initparams206.htm
HTH.

Adding online redo logs with standby database in place

Hi group,
I have decided to add one new member to my existing redo log groups and an additional redo log group to my primary database.
That change went ok without problems. I assumed that with standby_file_management=auto the equivalent online redo logs are created on the standby database. But this is not the case.
The documentation is unclear about this point and I did not find anything suitable on metalink. The docs suggest to cancel managed recovery on the standy, setting standby_file_management to MANUAL and then adding online logs, quote:
"To add an online redo log, use a SQL statement such as this:
SQL> ALTER DATABASE ADD STANDBY LOGFILE 'prmy3.log' SIZE 100K;"
This however - IMO - adds a new STANDBY redo log to the standby database, what I need is an ONLINE redo log.
Does anybody have some experience to share here?
Facts:
Solaris 8
Oracle 9.2.0.6
Thanks!
Martin

OK, for those who come across the same problem.
You need to create a new standby controlfile, copy it as well as any new online redo log from production to the standby environment.
Once the files are in place, start the standby as normal and open it read only to see if everything is ok:
startup nomount
alter database mount standby database;
alter database open read only
Only when there are no errors in your alert.log you are safe.
Martin

Asynch Hot Log mode does not use hot (online) redo logs

Version 10.2
We have just set up a test of the Asynch Hot Log replication according to Chap 16 of the Data Warehousing guide.
We can see data put into the change table. However, it seems that data gets written to the change table ONLY after a log switch. This would suggest that the capture process is not reading the online logs, but is only reading the archived logs.
I don't think this can be correct behavior because the docs indicate that Oracle "seamlessly switches" between the online and the archived redo logs.
Is there a flag or something to set to cause the online logs to be available to the capture process? Or is this a bug? Has anyone else observed this behavior?
Thanks for any insight.
-- Chris Curzon

According to the 10g Dataguard docs, section 2.5.1:
"Physical standby databases do not use an online redo log, because physical standby databases are not opened for read/write I/O."yes, those are used when database is open.
You should not perform any changes in Standby. Even if those exist online redo log files, whats the difficulty you have seen?
These will be used whenever you performed switchover/failover. So nothing to worry on this.
Is this a case of the STANDBY needing at least a notion of where the REDO logs will need to be should a failover occur, and if the files are already there, the standby database CONTROLFILE will hold onto them, as they are not doing any harm anyway?Then oracle functionality itself harm if you think in that way. When they not used in open then what the harm with that?
Standby_File_management --> for example if you add any datafile, those information will be in archives/redos once they applied on standby those will be added automatically when it is set to AUTO if its manual, then it creates a unnamed file in $ORACLE_HOME/dbs location later you have to rename that file and recovery need to perform .
check this http://docs.oracle.com/cd/B14117_01/server.101/b10755/initparams206.htm
HTH.

Cold backup with online redo logs

I am working on 10G in AIX for a single instance
It is just a general db backup & restore question, but I have something confused.
I am going to perform a cold backup with my ARCHIVELOG database.
No wonder why I perform a cold backup because it is a testing database which can suffer from data lost and down time during backup.
I read some guides. They all mentioned to backup all the datafiles and control files.
During the restoration, I have to copy all the backed up datafiles and control files to the default location.
Then Startup mount;
The last step before open the database is recover database until cancel;
For the acknowledgement, I have to do the command of recover database, because the online redo logs were not backed up, thus we have to recover it in order to reset the redo logs.
For my question,Would I be able to skip the command of recover database, then directly startup the database if I have backed up the online redo logs and copy the default location during the restoration?
However, I read many documents which mention that it is not suggested to backup the online redo logs. Is it just the case which ONLY applied in hot backup? Do you all think that for my case, cold backup for online redo logs is recommended?
Thanks all

jgarry wrote:
Edit: And never forget, those test databases are some developers production.Absolutely true according to my experience. Loosing the work of a payed developer is just as bad as loosing the work of a production system and may even be worse because it may not be possible to re-enter missing data into the system.
I think a cold backup is only suitable on special occasions, for instance, to relocate/copy the database to a different storage media, or if the database doesn't change or if loosing changes is absolutely irrelevant. Otherwise, put the database into archivelog mode and do a hot backup. After that you will also have alternative options which can make the restore and recovery of the database very easy and efficient, like flashback database, etc. but it will take substantial additional disk space.

Backup online redo log files

Hi All
Can you please explain for me the main reason that we do not have to backup the online redo log using RMAN ?
Thanks

The online redo logfiles are necessary to perform a complete recovery of the database. During database recovery, Oracle will apply the archived redo logfiles and online redo logfiles to roll the database forward and finally remove uncommitted transactions. If any of the online redo logfile group is active and missing, the database recovery will be incomplete and the database needs to be opened with restlogs, causing a new database incarnation.
You have to shutdown the datrabase to be able to perform a backup of the online redo logfiles, or find another method to create a time based snapshot of the data to prevent data movement while the redo logfiles are in use in order to keep datafile headers, controlfile and redo logfiles in sync. It is for that reason that you multiplex and mirror redo logfiles.

Whole database online + redo log backup

Hello all,
we are running SAP on a Oracle Database and doing a daily backup.
In the DBA Planing Calendar, we do have the action
Whole database online + redo log backup
What exactly does that mean?
Thanks,
Anne

This backup will save the CONTENT of the database only, not the database software itself.
To get a full consistent backup you need to backup more things if you want to have everything - depending on the operating system:
On Unix you will need to backup the software directory (/oracle*, oraInventory, oratab (depending on the location)) etc.
On Windows you will need to backup <letter>:\oracle, the registry keys and more things.
However, in case of a recovery you can also install the software after an OS installation and then restore it from tape.
Markus

Online redo logs in Flash Recovery Area

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