What is the purpose of standby redo log files

Hi,
What is the purpose of the standby redo log files in DR?
what if the standby redo log files are created? or else not created?
Please explain
Thanks

3.1.3 Configure a Standby Redo LogA standby redo log is required for the maximum protection and maximum availability modes and the LGWR ASYNC transport mode is recommended for all databases. Data Guard can recover and apply more redo data from a standby redo log than from archived redo log files alone.
You should plan the standby redo log configuration and create all required log groups and group members when you create the standby database. For increased availability, consider multiplexing the standby redo log files, similar to the way that online redo log files are multiplexed.>
Reference http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/create_ps.htm#i1225703
HTH
Anand

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Unassigned Status Of Standby Redo Log Files

I created 2 standby redo log groups, and use LGWR in primary site to
transfer redo data, all are good. But when I query the V$STANDBY_LOG
view, I found that the status column of my both standby redo logs is UNASSIGNED".
also sequence#
THREAD# and all others are 0 and 0.
Any explains.

Thanks for the reply Sophie. I did perform log switch at my primary site but the status of standby redo log files remained unassinged. I am pasting here the message in my Alert Log file may be that can help you to diagonose the problem.
ALTER DATABASE SET STANDBY DATABASE PROTECTED
Tue Jul 26 15:35:18 2005
Completed: ALTER DATABASE SET STANDBY DATABASE PROTECTED
Tue Jul 26 15:35:22 2005
ALTER DATABASE OPEN
Tue Jul 26 15:35:23 2005
LGWR: Primary database is in CLUSTER CONSISTENT mode
LGWR: Primary database is in MAXIMUM PROTECTION mode
LGWR: Destination LOG_ARCHIVE_DEST_1 is not serviced by LGWR
LNS0 started with pid=18
Tue Jul 26 15:35:28 2005
LGWR: Error 16086 verifying archivelog destination LOG_ARCHIVE_DEST_2
LGWR: Continuing...
Tue Jul 26 15:35:28 2005
Errors in file e:\oracle\admin\test\bdump\test_lgwr_1864.trc:
ORA-16086: standby database does not contain available standby log files
LGWR: Error 16086 disconnecting from destination LOG_ARCHIVE_DEST_2 standby host 'TESTstdb'
LGWR: Minimum of 1 applicable standby database required
Tue Jul 26 15:35:28 2005
Errors in file e:\oracle\admin\test\bdump\test_lgwr_1864.trc:
ORA-16072: a minimum of one standby database destination is required
LGWR: terminating instance due to error 16072
Instance terminated by LGWR, pid = 1864

Standby redo log file

Hi,
From oracle document i know in the standby side the RFS process writes to Standby redo log file -> archive log and the MRP procees applys the archive logs to the standby database.
my question is ,if we dont create standby redo log file what happens?

Hello;
When redo is received by an RFS on the standby , the RFS process writes the redo data into archived redo logs or optionally to the SRL.
Standby Redo Logs is where the RFS process at your Standby database writes incoming redo, they help performance because the RFS does not have to create the Archive log file.
Standby redo logs are a component of the Data Guard setup. They should be the same size as the redo logs on the Primary.
Standby Redo Logs do not not to be multiplexed.
I would create SRL them on both the Primary and the Standby. Think of it as one database in either Standby or Primary Mode. If you have to switchover you still need them.
If you have SRL's setup and need to do either a failover or switchover it should occur faster and safer.
Best Regards
mseberg

Use of standby redo log files in primary database

Hi All,
What is the exact use of setting up standby redo log files in the primary database on a data guard setup?
any good documents?

A standby redo log is required for the maximum protection and maximum availability modes and the LGWR ASYNC transport mode is recommended for all databases. Data Guard can recover and apply more redo data from a standby redo log than from archived redo log files alone.
You should plan the standby redo log configuration and create all required log groups and group members when you create the standby database. For increased availability, consider multiplexing the standby redo log files, similar to the way that online redo log files are multiplexed.
refer the link,and Perform the following steps to configure the standby redo log.:-
http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/create_ps.htm#i1225703
If the real-time apply feature is enabled, log apply services can apply redo data as it is received, without waiting for the current standby redo log file to be archived. This results in faster switchover and failover times because the standby redo log files have been applied already to the standby database by the time the failover or switchover begins.
refer the link
http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/log_apply.htm#i1023371

Dataguard lost both Primary redo log and standby redo log files

Hi,
I am new to data guard, i came acorss a scenario where we loose both primary redo log file and standby redo log files.
Can someone please help me understand how to recover from this situation.
Thanks!

>loose both primary redo log file and standby redo log files
We have to be very clear.
There are (set A) online redo log files and (set B) standby redo log files at (location 1) Primary and (location 2) Standby.
The standby redo log files, depending on the configuration, aren't strictly mandatory. The standby can be applying redo without online redo log files present as well, depending on how it was setup.
So, the question is : Did you lose online redo log files at the primary ? Didn't the primary shutdown itself then ? If so, you have to do an incomplete recovery at the primary OR switch over to the standby (which may or may not have received the last transaction, depending on how it was configured and operating) OR restore from the standby (again, with possible loss of transactions) to the primary.
Hemant K Chitale

Do I need to create new group for standby redo log files?

I have 10 group of redo log files with 2 members for each group for my primary database , Do I need to create new group for standby redo log files for the standby database
Group#     Members
==============
1              2
2              2
3             2
4             2
5             2
6             2
7             2
8             2
9             2
10           2
If So, The following statment is correct? or nto
ALTER DATABASE ADD STANDBY LOGFILE GROUP 1 ('D:\Databases\epprod\StandbyRedoLog\REDO01.LOG',D:\Databases\epprod\StandbyRedoLog\REDO01_1.LOG');
please correct me if am doin mistake
becuase when I issue the statment I getting error message sayin the group is already created.

Thanks John
I just find the answer
Yes, it's recomeded to add new group , for instnace If I have 10 group from 1 to 10 then the standby shoudl be from 11 to 20
Thanks I found the answer.

Dataguard Solution for standby redo log file groups

Respected Experts,
My database version is 10.2.0.1.0 and Red Hat 5 os.I want to create a standby database using RMAN.
Can any one help me with the full steps.And i'm also confuse about number of standby redo log file members
need to be created.
Thanks and Regards
Monoj Das

My database version is 10.2.0.1.0 and Red Hat 5 os.I want to create a standby database using RMAN.To configure standby either you can use duplicate target database for standby
or
1) restore standby controlfile
2) mount standby database
3) restore database
and configure standby paraemter then start MRP, will do.
http://docs.oracle.com/cd/B19306_01/server.102/b14239/create_ps.htm
Can any one help me with the full steps.And i'm also confuse about number of standby redo log file members
need to be created.It depends which parameter you want to use, if you mention log_archive_dest_2='service ARCH ' then no need to create any standby redo log file groups,
If you use log_archive_dest_2='service LGWR ' here transport will be in terms of redo and you need standby redo log files on standby database. Which is realtime.
When you use LGWR, data lost will be less if in case of any online redo log file lost. which is recommended.
HTH.

How do look if i have Standby Redo Log files

How do look if i have Standby Redo Log files
example of creating them..

To check existence of Standby Redo Log Files:
SQL> v$standby_log
Name                                      Null?    Type
----------------------------------------- -------- ---------------------------- GROUP#                                             NUMBER
DBID                                               VARCHAR2(40)
THREAD#                                            NUMBER
SEQUENCE#                                          NUMBER
BYTES                                              NUMBER
USED                                               NUMBER
ARCHIVED                                           VARCHAR2(3)
STATUS                                             VARCHAR2(10)
FIRST_CHANGE#                                      NUMBER
FIRST_TIME                                         DATE
LAST_CHANGE#                                       NUMBER
LAST_TIME                                          DATE
SQL> select * from v$standby_log;
no rows selected
SQL>To Create a Standby Redo Log file:
SQL> alter database add standby logfile group 11 ('/u01/app/test.log') size 5m;
Database altered.
SQL> set line 10000
SQL> select * from v$standby_log;
    GROUP# DBID                                        THREAD# SEQUENCE#      BYTES       USED ARC STATUS     FIRST_CHANGE# FIRST_TIM LAST_CHANGE# LAST_TIME
        11 UNASSIGNED                                        0          0    5242880        512 YES UNASSIGNED              0                      0
SQL>and this is how you drop:
SQL> alter database drop standby logfile group 11;
Database altered.
SQL> ! rm /u01/app/test.log
SQL>Asif Momen
http://momendba.blogspot.com
Edited by: Asif Momen on Mar 16, 2010 1:32 PM
Included DROP example

Standby Redo Log Files ?

Hi Everyone,
Today after reading two different sources for Standby Protection Modes i found myself puzzled and stuck. One of the article from Burleson.com says 'Oracle supports the standby redo logs on a logical standby database and can now be configured in maximum data protection modes such as MAXIMUM PROTECTION ...'
On the other hand on some of the blogs and other resources to read, i found it something opposite to what Burleson Consulting posted on their website.
[http://4.bp.blogspot.com/-t0G_-xc8EAs/Tpvx9w2t8oI/AAAAAAAAAN4/Jw3U9s89Wtk/s1600/final.JPG|http://4.bp.blogspot.com/-t0G_-xc8EAs/Tpvx9w2t8oI/AAAAAAAAAN4/Jw3U9s89Wtk/s1600/final.JPG]
or
Blog from Jeff Hunter
[http://www.idevelopment.info/data/Oracle/DBA_tips/Data_Guard/DG_3.shtml|http://www.idevelopment.info/data/Oracle/DBA_tips/Data_Guard/DG_3.shtml]
Minimum Requirements for Data Protection Modes
     Maximum Protection      Maximum Availability      Maximum Performance
Redo Archival Process      LGWR      LGWR      LGWR or ARCH
Network Transmission Mode SYNC      SYNC      ASYNC when using LGWR process. Not applicable when using ARCH process.
Disk Write Option      AFFIRM      AFFIRM      NOAFFIRM
Standby Redo Logs Required?      Yes      Required for physical standby databases only (Standby redo logs are not supported for logical standby databases.)      Required for physical standby databases using the LGWR process.
Database Type      Physical only      Physical and Logical      Physical and Logical
Please help me to find true between the two.
Or please provide any doc to read.
Thanks
Prashant Dixit

Maximum Protection Maximum Availability Maximum PerformanceDepends on Business requirement, By default Performance[most of the clients]
Redo Archival Process ? ? ?LGWR recommended in Max performance
Network Transmission Mode ? ? ?Depends. If max performance asynchronous
Disk Write Option ? ? ?Not clear
Standby Redo Logs Required? ? ? ?If real time apply - YES
Database Type ? ? ?not clear,
Assuming physical or logical? --Depends on requirement , Preferably Physical.

Standby Redo Log Files and Directory Structure in Standby Site

Hi Guru's
I just want to confirm, i know that if the Directory structure is different i need to mention these 2 parameter in pfile
on primary site:
DB_CONVERT_DATAFILE='standby','primary'
LOG_CONVERT_DATAFILE='standby','primary'
On secondary Site:
DB_CONVERT_DATAFILE='primary','standby'
LOG_CONVERT_DATAFILE='primary','standby'
But i want to confirm this wheather i need to issue the complete path of the directory in both the above paramtere:
like:
DB_CONVERT_DATAFILE='/u01/oracle/app/oracle/oradata/standby','/u01/oracle/app/oracle/oradata/primary'
LOG_CONVERT_DATAFILE='/u01/oracle/app/oracle/oradata/standby','/u01/oracle/app/oracle/oradata/primary'
Second Confusion:-
After transferring Redo Standby log files created on primary and taken to standby on the above mentioned directory structure and after restoring the backup of primary db alongwith the standby control file will not impact the physical standby redo log placed on the above mentioned location.
Thanks in advance for your help

Hello,
Regarding your 1st question, you need to provide the complete path and not just the directory name.
On the standby:
db_file_name_convert='<Full path of the datafiles on primary server>','<full path of the datafiles to be stored on the standby server>';
log_file_name_convert='<Full path of the redo logfiles on primary server>','<full path of the redo logfiles on the standby server>';
Second Confusion:-
After transferring Redo Standby log files created on primary and taken to standby on the above mentioned directory structure and after restoring the backup of primary db alongwith the standby control file will not impact the physical standby redo log placed on the above mentioned location.
How are you creating the standby database ? Using RMAN duplicate or through the restore/recovery options ?
You can create the standby redo logs later.
Regards,
Shivananda

Require 9i Primary and Standby redo logs files same size?

Hi,
We have 9.2.0.6 Oracle RAC (2 node) and configured data guard (physical standby).
I want to increase redo log files size, but i can't this do same time primary and standby side.
Is there a rule, primary and standby database instances have same size redo log files?
If I increase only primary redo log files, is there any side effect? However I try this issue on test system. I increased all primary redo log files(if status='INACTIVE' drop redo log group and add redo log group, switch logfile,...)
, but i couldn't changed standby side. So the system is work well. Is this correct solution or not? How can i increase both sides redo log files?
Thank you for helps..

Thank you for your helps.. I found this issue answer:
http://download-west.oracle.com/docs/cd/B19306_01/server.102/b14239/manage_ps.htm#i1010448
Consequently, when you add or drop an online redo log file at the primary site, it is important that you synchronize the changes in the standby database by following these steps:
If Redo Apply is running, you must cancel Redo Apply before you can change the log files.
If the STANDBY_FILE_MANAGEMENT initialization parameter is set to AUTO, change the value to MANUAL.
Add or drop an online redo log file:
To add an online redo log file, use a SQL statement such as this:
SQL> ALTER DATABASE ADD LOGFILE '/disk1/oracle/oradata/payroll/prmy3.log' SIZE 100M;
To drop an online redo log file, use a SQL statement such as this:
SQL> ALTER DATABASE DROP LOGFILE '/disk1/oracle/oradata/payroll/prmy3.log';
Repeat the statement you used in Step 3 on each standby database.
Restore the STANDBY_FILE_MANAGEMENT initialization parameter and the Redo Apply options to their original states.
bye..

Oracle standby/redo log file shipping keeps needing logs re-registering

Hi
We have Log File Shipping enabled and the prod system ships redo logs over to the LFS server. It's kept 24 hours behind. It usually ships the logs (and I believe automatically registers them) without issue.
EXCEPT - it keeps complaining about missing redo log files.
The file is usually there; but just needs registering with:
alter database register or replace logfile '/oracle/S1P/saparch/S1Parch1_636443_654987192.dbf';
(we found if we left out the 'or replace' it takes a very long time or even hangs)
It then plods on and applies the next... can go for another 2 or 3... or 20... but then often gets stuck again, and you need to register the next.
Can spend whole days on this...!!
We did try running a script to register the next 1365 redo logs! It failed on 4, so I ran it again... it worked on those 4, but turned up 3 others it had worked with before! HUH?!? So manually did those 3 ... fine... it carried on rolling forward... but got stuck after 10 minutes again when it hit another it reckoned needed registering (we'd already done it twice!!).
Any ideas?
Ross

Hi
We have Log File Shipping enabled and the prod system ships redo logs over to the LFS server. It's kept 24 hours behind. It usually ships the logs (and I believe automatically registers them) without issue.
EXCEPT - it keeps complaining about missing redo log files.
The file is usually there; but just needs registering with:
alter database register or replace logfile '/oracle/S1P/saparch/S1Parch1_636443_654987192.dbf';
(we found if we left out the 'or replace' it takes a very long time or even hangs)
It then plods on and applies the next... can go for another 2 or 3... or 20... but then often gets stuck again, and you need to register the next.
Can spend whole days on this...!!
We did try running a script to register the next 1365 redo logs! It failed on 4, so I ran it again... it worked on those 4, but turned up 3 others it had worked with before! HUH?!? So manually did those 3 ... fine... it carried on rolling forward... but got stuck after 10 minutes again when it hit another it reckoned needed registering (we'd already done it twice!!).
Any ideas?
Ross

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.

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,
Smith

Example:
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

What's the command to dump archived log file?

Could someone share if you remember? I forgot the syntax. Thanks alot.

Are you referring to extracting data from the archive log files? If so, you should refer to this Using LogMiner.

What is the purpose of standby redo log files

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