Standby redolog files

Hi
I think standby redolog files are not required if I open the physical standby database in read/write mode by using flashback database techonology. Kindly let me know if I am wrong.

sat1980 wrote:
Hi,
Thanks for coming back on this, sorry for confusing with my question, I will re-frame my question as
"I think standby redolog files are not required on PRODUCTION, if I open the physical standby database in read/write mode by using flashback database techonology", basically I wanted to know that standby redologs on production and standby are required only when switch over are switch back are done.If you would open(using any technology wether flashback or without it) your physical standby database (keeping production also in open mode) that means both these database are now independent and redo logs(archive logs) of any of the database cannot be applied to each other. Hence there would not be any use of standby redo log files.
Standby redo logs are used to get the redo files(data) on the standby database from the primary even if the redo log is not archived on primary. Hence if you want that feature in your standby database it is necessary to have standby redo log files.
Yes standby redo log files are not required for production but oracle recommends it to make smooth switch over.
Regards
Anurag

Similar Messages

Configuring data guard: how many standby redolog do I need?

Hi all, I want to add a standby databse to my RAC test environment but I don't understanad how many redolog I need.
The main db is a 2 node RAC (10.2.0.4.0); every node has 3 log groups; every log group has 2 logfile (every log group is multiplexed on DG_DATA1/ASR/ and FLASH_RECOVERY_AREA/ASR/ )
The standby db will have all its datafile on the same filesystem, so I already configured the trasnslations parameters:
DB_FILE_NAME_CONVERT='/opt/oracle/app/oracle/oradata1/ASRSB','+DG_DATA1/ASR','/opt/oracle/app/oracle/oradata2/ASRSB','+FLASH_RECOVERY_AREA/ASR'
LOG_FILE_NAME_CONVERT='/opt/oracle/app/oracle/oradata1/ASRSB','+DG_DATA1/ASR','/opt/oracle/app/oracle/oradata2/ASRSB','+FLASH_RECOVERY_AREA/ASR'
Replication via rman works well, but I have to manually add the standby redolog on the standby db and which formula to use to calculate the number of the standby redolog needed. Which is the correct formula between :
1)
# of standby log = ( # of redolog files + 1) * # of thread = (6 +1)*2 = 14 standby redolog files
2)
# of standby log = ( # of redolog groups + 1) * # of thread = (3 +1)*2 = 8 standby redolog files
thanks,
andrea

Andrea,
I think 8 should be the answer on your question. Because you have 3 log groups and 2 threads therefore (3+1)*2 = 8.
According to the documentation :
http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/create_ps.htm#SBYDB00426
Minimally, the configuration should have one more standby redo log file group than the number of online redo log file groups on the primary database. However, the recommended number of standby redo log file groups is dependent on the number of threads on the primary database. Use the following equation to determine an appropriate number of standby redo log file groups:
(maximum number of logfiles for each thread + 1) * maximum number of threads
I think you may get confused with maximum number of logfiles. But sometimes logfile is used as a synonym to log group. The actual log group files are usually called log members. (for instance MAXLOGFILES parameter specifies the maximum number of log groups and MAXLOGMEMBERS specifies the maximum number of members for each group).
Each additional member in a redo log group is just a multiplexed copy. You can also consider multiplexing the standby redo log files, the same why you do for redo log members.
In order to learn more about the usage, benefits and limitations of Standby Redo Logs (SRL) you can refer to Metalink Note 2193444.1.
I hope this helps.
--Mihajlo

Standby redolog creation

Hi,
At the time of physical standby DB creation Oracle doc says that...
3.1.3 Configure a Standby Redo Log
Example 3-1 Adding a Standby Redo Log File Group to a Specific Thread
The following statement adds a new standby redo log file group to a standby database and assigns it to THREAD 5:
SQL> ALTER DATABASE ADD STANDBY LOGFILE THREAD 5
2> ('/oracle/dbs/log1c.rdo','/oracle/dbs/log2c.rdo') SIZE 500M;
Is this logfiles created in the primary DB and the directory structure is in primary DB?
If yes then, how under section 5.1 Introduction to Redo Transport Services figure 5-1shows standby redolog files are showing in standby DB?
So shall I create standby redolog in both DBs? or only in primary DB?
I need your input to clear this confusion please.
regards

Hello,
You SHOULD create your standby redo log files on both your current primary AND your current standby.
You never know, one day the current primary might be the current standby and the current standby your now current primary!
jason
http://jarneil.wordpress.com/2007/11/18/standby-redo-logs/

Which standby redolog directory is OK?

I have tried many times to configure a physical standby database manually. But no once succeed. The error message is "ORA-02778: Name given for the log directory is invalid." I don't know which standby redolog directory should I specify?
The rodolog directory of primary database is 'C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL9\REDO01.LOG'.
When I specify one of follow directory for a standby redolog file, the system always show previous error message:
'C:\ORACLE\PRODUCT\10.2.0\ORADATA\STDBY3\REDO01.LOG'
'\ORACLE\PRODUCT\10.2.0\ORADATA\STDBY3\REDO01.LOG'
'C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL9\REDO05.LOG'
Only add log file,don't specify it's directory.
10g-10.2.0 on WindowsXP,only one member per group.
primary and stanby database on same host.
Message was edited by:
frank.qian
Message was edited by:
frank.qian
Message was edited by:
frank.qian

Thank you for consideration.
I will post the steps later.
Firstly,I want to ask you some questions:
---In the documentation of 10g(10.2), the step of adding standby redo logfile is listed before mounting standby database.(seeOracle® Data Guard Concepts and Administration: 3.1.3 Configure a Standby Redo Log). But in the documentations of 10g(10.1) and 11g(11.1), this step is listed after the mounting of dtandby database. Why not same. I have checked other person's statements. Most of them prefer the latter.Is 10g(10.2)'s documentation wrong? I create standby database according to the steps listed in 10g(10.2) documentation.
---When I create the stanby database, the parameter LOCK_NAME_SPACE was not edited in standby Pfile, Because this step is not listed in the documentation.
Message was edited by:
frank.qian
Message was edited by:
frank.qian

Standby redologs on Physical Standby

Hi all,
Oracle 10gR2
I'd already created Standby redolog files @Primary then take rman backup of datafiles,archivelogfiles and control file for restoration standby
do i still need to create standby redolog files @Physical standy (after rman restoration completes)
RMAN> DUPLICATE TARGET DATABASE FOR STANDBY NOFILENAMECHECK;
Kindly suggest.
Regards & thanks to all
Muhammad Shakeel Azeem

Hello;
No.
If you create the SRL on the Primary and then take an RMAN backup for duplicate they will be part of that backup.
Example :
RMAN RUN {
allocate channel d1 type disk;
backup format '/u01/backups/PRIMARY/df_t%t_s%s_p%p' database;
sql 'alter system archive log current';
backup format '/u01/backups/PRIMARY/al_t%t_s%s_p%p' archivelog all;
backup current controlfile for standby format '/u01/backups/PRIMARY/sb_t%t_s%s_p%p';
release channel d1;
}Restore example
run {
allocate channel C1 device type disk;
allocate auxiliary channel C2 device type disk;
duplicate target database for standby nofilenamecheck;
}Best Regards
mseberg
Double Check ( To be clear on Oracle 11, but I think it work the same on 10 )
I checked my test Standby which I created using RMAN- The SRL's are there.
But you are 10 so use this to check for them :
select * from v$standby_log;If they are not there and the database is mounted create them as follows :
ALTER DATABASE ADD STANDBY LOGFILE GROUP 4 '/u01/app/oracle/oradata/PRIMARY/redo04.log' SIZE 100M;Change path, size, names and groups as needed.
Edited by: mseberg on Mar 24, 2012 8:29 AM
Edited by: mseberg on Mar 24, 2012 8:32 AM

How can I add Redolog files in standby

Hi,
I am about to create standby database in standard edition of Oracle9i through RMAN I can't find any entry regarding Redologs in DUPLICATE command can I add redolog after creating standby database or standby database doesn't need redologs, plz let me clear.
Thanks in advance.
Khawar

Hi,
you can add redolog files for variety of purposes,and this is not mendetory for creating stdby databases.
anyway you can use these commands which are give below.
ALTER DATABASE ADD STANDBY LOGFILE
('/oracle/dbs/log1c.rdo','/oracle/dbs/log2c.rdo') SIZE 500K;
You can also specify a number that identifies the group using the GROUP option:
ALTER DATABASE ADD STANDBY LOGFILE GROUP 10
('/oracle/dbs/log1c.rdo','/oracle/dbs/log2c.rdo') SIZE 500K;
thnks.

How to create a standby redolog from rac to non rac ??

Hi,
How to create a standby redolog from rac to non rac DR setup..???
in rac we can create with specifying thread number for each instances..... but this will be replicating to standby ....so how this will act/create on single DR??
pls help

854393 wrote:
Thanks Shivanandha,
(maximum number of logfiles for each thread + 1) * maximum number of threads
Using this equation reduces the likelihood that the primary instance's log writer (LGWR) process will be blocked because a standby redo log file cannot be allocated on the standby database. For example, if the primary database has 2 log files for each thread and 2 threads, then 6 standby redo log file groups are needed on the standby database.In maximum performance mode you can keep same number of redo logs but having one more redo log member for each thread is recommended and mandtory for other protection modes.
How to create a standby redolog from rac to non rac DR setup..???
in rac we can create with specifying thread number for each instances..... but this will be replicating to standby ....so how this will act/create on single DR??pls help
Yes, even your DR is RAC or non-RAC, you must have both threads, because each instance information exist on own thread, So to perform redo transition from both the instances, you must have both standby redo log threads even though if it is non an RAC DR.
Hope This helps.

Standby log files

I want to convert our old script based primary /standby database into a dataguard config using the LGWR as log transport.
I already have old log files on the standby database, but the data in them is from 2004. Not entirely interesting since the database gets recovered from the arch log files every night.
Point is, can I use these as standby log files, or do I have to (somehow) drop these and re-create new standby logfiles. I cant drop them anyway since when I try, I get "ORA-01624, log 1 needed for crash recovery". (Like h*ll, since the data is older than Noah).
Will these just get re-written?
null
null

Note:219344.1 This note from metalink gives "Usage, Benefits and Limitations of Standby Redo Logs (SRL)".
Standby Redo Logs are only supported for the Physical Standby Database in
Oracle 9i and as well for Logical Standby Databases in 10g. Standby Redo Logs
are only used if you have the LGWR activated for archival to the Remote Standby
Database.
The great Advantage of Standby Redo Logs is that every Entry written into
the Online RedoLogs of the Primary Database is transfered to the Standby
Site and written into the Standby Redo Logs at the same time; threfore, you
reduce the probability of Data Loss on the Standby Database.

STATUS of STANDBY REDOLOG

Hello, masters
I have configured a replication environment using real-time capture downstream and everything has gone well. As I have in my source database three groups of redologs, before I created the capture process I add four groups of standby redolog in the downstream database. That is, one more than the number of online redolog present in my source database.
But sometime, when I do the following query:
SELECT ARCHIVED, STATUS FROM V$STANDBY_LOG;
It returns the following for all the standby redolog groups
ARCHIVED STATUS
NO ACTIVE
Because of the above, the capture process behaves like an archived-log downstream capture process. In other words, when a redolog group is archived at the source database, the capture process does his work.
When I look in the alert file I found this message
ORA-16014: log 5 sequence# 6980 not archived, no available destinations
And the trace file:
DDE: Problem Key 'ORA 312' was flood controlled (0x1) (no incident)
ORA-00312: online log 5 thread 1: '+BD4/stra/onlinelog/group_5.271.712605279'
ORA-00312: online log 5 thread 1: '+BD3/stra/onlinelog/group_5.261.712605279'
*** 2010-05-09 06:48:24.805 11367 kcrr.c
Impossible archival state:10
Thanks in advance

Yes I do
ALTER SYSTEM SET LOG_ARCHIVE_DEST_2='LOCATION=+BD7/ VALID_FOR=(STANDBY_LOGFILE,PRIMARY_ROLE)';

How can i drop the redolog File

hello ,
I was installing oracle 10g on windows using DBCA. The problem is that i made three group of redolog size 1M. When DBCA was creating the database i got an error msg that "Size of redo log is less "But i ignored that error.
Ater that the database was created and i got a warning open the datbase using resetlogs.
The datbase is created but in Redolog file was not there(Physical files).
now i mounted the database. At that time the 3rd Redolog grp was active so i dropped the 1st n 2nd grp and created with 8MB.
but to drop 3rd grp i want swicth the logfile but without opening the datbase it is not possible.
and with the current size of 3rd redolog grp(Becoz of size) it is not possible to open the database.
So plz tell me how can i
1) How can i switch the logfile grp
2) drop the 3rd redolog group
thanx in advance
Ashish

Well, you can recreate ctlfile :
SQL> startup mount
ORACLE instance started.
Total System Global Area 135339876 bytes
Fixed Size                   454500 bytes
Variable Size             109051904 bytes
Database Buffers           25165824 bytes
Redo Buffers                 667648 bytes
Database mounted.
SQL> alter database backup controlfile to trace;
Database altered.
SQL> shutdown immediate
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.In the file generated, take the step #2, and change the size of redolog files. And run it :
SQL> CREATE CONTROLFILE REUSE DATABASE "DEMO9I" RESETLOGS NOARCHIVELOG
2 -- SET STANDBY TO MAXIMIZE PERFORMANCE
3      MAXLOGFILES 50
4      MAXLOGMEMBERS 5
5      MAXDATAFILES 100
6      MAXINSTANCES 1
7      MAXLOGHISTORY 226
8 LOGFILE
9    GROUP 1 'E:\ORACLE\ORADATA\DEMO9I\REDO01.LOG' SIZE 110M, --I changed it, it was 100M
10    GROUP 2 'E:\ORACLE\ORADATA\DEMO9I\REDO02.LOG' SIZE 110M,--I changed it, it was 100M
11    GROUP 3 'E:\ORACLE\ORADATA\DEMO9I\REDO03.LOG' SIZE 110M--I changed it, it was 100M
12 -- STANDBY LOGFILE
13 DATAFILE
14    'E:\ORACLE\ORADATA\DEMO9I\SYSTEM01.DBF',
15    'E:\ORACLE\ORADATA\DEMO9I\UNDOTBS01.DBF',
16    'E:\ORACLE\ORADATA\DEMO9I\CWMLITE01.DBF',
17    'E:\ORACLE\ORADATA\DEMO9I\DRSYS01.DBF',
18    'E:\ORACLE\ORADATA\DEMO9I\EXAMPLE01.DBF',
19    'E:\ORACLE\ORADATA\DEMO9I\INDX01.DBF',
20    'E:\ORACLE\ORADATA\DEMO9I\ODM01.DBF',
21    'E:\ORACLE\ORADATA\DEMO9I\TOOLS01.DBF',
22    'E:\ORACLE\ORADATA\DEMO9I\USERS01.DBF',
23    'E:\ORACLE\ORADATA\DEMO9I\XDB01.DBF',
24    'E:\ORACLE\ORADATA\DEMO9I\TBS_TST_01.DBF'
25 CHARACTER SET AL32UTF8
26 ;
Control file created.
SQL> ALTER DATABASE OPEN RESETLOGS;
Database altered.
SQL> ALTER TABLESPACE TEMP ADD TEMPFILE 'E:\ORACLE\ORADATA\DEMO9I\TEMP01.DBF' REUSE;
Tablespace altered.
SQL> HTH,
Nicolas.

Standby redologs mandatory

Hi,
I'm new in data guard feature.
I did create a physical standby and all works perfect. The archive are shipped and applied.
I even sometime put the standby in read only mode in the morning and in the evening back in recovery mode.
I just have some need of a point to clear.
I don't have any standby redolog and all works fine. This looks then not primordial to have ?
Is it a livable system like this ? I mean that I plan to use my standby for a read only database to put some workload off the primary (for statistics purpose).
Working on AIX with Oracle 10.2
Thanks,

Let me explain why you always need them even with ASYNC or ARCH transport modes with Maximum Performance. They are mandatory for SYNC otherwise you will not be running in the protection mode that SYNC is for, Maximum Availability or Maximum Protection. And as you know, in Maximum Protection if you do not have them the Primary will not open.
But that aside, this is why you need them even in Maximum Performance.
For Performance:
When your primary database switches online log files, the LNS (or ARCH if you are in 10g and using ARCH transport) has to tell its corresponding RFS process at the standby to close the current sequence and start the next one. If you do not have standby redo log files that RFS process has to make the LNS/ARCH wait until it has created and initialized an archive log of the appropriate size. This can take awhile depending on the size of your online redo log files. If you have standby redo log files then the RFS merely opens one and tells the LNS/ARCH it is ready to receive redo.
For Protection:
When redo is being shipped to the standby and written to an SRL, that redo will be there when the Primary fails and you need to protect your data. If that redo is in an archive log then no matter how much was written to the archive log at the standby, it is all (100%) thrown away when the connection to the primary goes away and the RFS exits. So if you wrote 49 or 50MB or 499 or 500MB, all that redo is lost.
For Concurrency:
And if you do not care about protection the only reason I can think of why that would be is that the standby is an Active Data Guard standby in a reader farm (where it would be likely that a switchover or failover would not occur). And if it is an Active Data Guard standby (for which you paid money to use) then you would want the data in the standby to be as current with the primary as possible, otherwise why have it? And in that case you would want to use real time apply to get that data available to your readers as fast as possible. You cannot do real time apply without standby redo log files.
So, no matter what side of the road you walk on, there really is no argument that is valid for not using standby redo log files. Sure the standby will 'work' without them but so will my car without seat belts, doors or lights. But who would drive a car like that when my life depended on it?
Larry

Can change the size of the redolog files while the database is running.

How the size of the redolog files will hurt your database performance ?
Can change the size of the redolog files while the database is running in oracle 9i. ?
What will be its impact on the standby database ?
Thanks in advance.

redo logs that are too small can cause waits on the switches for heavily utilized systems. logs that are too large are a pain the a$$ during recovery. check v$loghist to see how often switches occur - an average of 20 minutes is good; if you have many switches happening back-to-back, that's a bad sign.
you can change the sizes while the db is up. choose a redo group that is INACTIVE, drop it, delete the files, and recreate it with larger files. then force a switch ("alter system switch logfile;"), and do another inactive group. I actually prefer to do as many switches as necessary to make the new group active so I can verify that I didn't screw up before dropping the next group.
not sure of impact on standby database.

How to read the contents of redolog files?

Hi,
I would want to read the contents of the redolog files on my database.
Actually, I can't because these files are binary files*. I would want to know if there is a way to read these redolog files , if for example Oracle has tools to learn these redolog files.
Thanks.

In order to read the content of the Redo Log files, you should use Logminer Utility
Please refer to the documentation for more information:
[Using LogMiner to Analyze Redo Log Files|http://download.oracle.com/docs/cd/B19306_01/server.102/b14215/logminer.htm#SUTIL019]
Kamran Agayev A. (10g OCP)
http://kamranagayev.wordpress.com
[Step by Step install Oracle on Linux and Automate the installation using Shell Script |http://kamranagayev.wordpress.com/2009/05/01/step-by-step-installing-oracle-database-10g-release-2-on-linux-centos-and-automate-the-installation-using-linux-shell-script/]

Standby redologs in the standby database

Hi All,
I am preparing the standby database using RMAN creation steps. I am confusing in one area. I have standby redologs in the Primary server. When we issue the duplicate target database for standby dorecover nofilenamecheck command, is it create the standby redologs in the standby database or not ?
please cofirm
Thanks
Shiju

Hi,
no, you must to create standby redo logs manually.
This script may help you
select 'alter database add standby logfile '''||
regexp_substr(MEMBER,'/.+/')||'stdby_'||
regexp_replace(member,regexp_substr(MEMBER,'/.+/'),'')||
''' size '||bytes||';' "Create Standby redo"
from v$logfile lf , v$log l
where l.group# = lf.group#
union all
select 'alter database add standby logfile '''||
regexp_substr(MEMBER,'/.+/')||'stdby_redo0'||(select max(group#)+1 from v$log)||'.rdo'||
''' size '||bytes||';' "Create Standby redo"
from v$logfile lf , v$log l
where l.group# = lf.group#
and rownum <=2
Create Standby redo
alter database add standby logfile '/oracle/redo/prod1/stdby_redo03a.rdo' size 52428800;
alter database add standby logfile '/oracle/redo/prod1/stdby_redo03b.rdo' size 52428800;
alter database add standby logfile '/oracle/redo/prod1/stdby_redo02a.rdo' size 52428800;
alter database add standby logfile '/oracle/redo/prod1/stdby_redo02b.rdo' size 52428800;
alter database add standby logfile '/oracle/redo/prod1/stdby_redo01a.rdo' size 52428800;
alter database add standby logfile '/oracle/redo/prod1/stdby_redo01b.rdo' size 52428800;
alter database add standby logfile '/oracle/redo/prod1/stdby_redo04.rdo' size 52428800;
more
http://www.pythian.com/news/581/oracle-standby-redo-logs
Regards,
Tom
http://asktom.cz

All redolog files lost in oracle 8i

Hi,
i had a disk corruption where i lost all redolog files and my db was down how i can make db up.
workaround:
in os level i manually created the lost redo log files (same path what was earlier):
sql>startup mount;
sql>recover database untill cancel;
sql>alter database open resetlogs;
is it works ?

Hi,
i foolowed what you said .removing the files you manually created,
SQL> startup mount;
ORACLE instance started.
Total System Global Area 488082184 bytes
Fixed Size 731912 bytes
Variable Size 268435456 bytes
Database Buffers 218103808 bytes
Redo Buffers 811008 bytes
Database mounted.
SQL> recover database until cancel;
ORA-00279: change 1578125068 generated at 03/06/2009 06:22:35 needed for thread
1
ORA-00289: suggestion : /oratranslog/archive/1_34930.dbf
ORA-00280: change 1578125068 for thread 1 is in sequence #34930
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
ORA-00308: cannot open archived log '/oratranslog/archive/1_34930.dbf'
ORA-27037: unable to obtain file status
SVR4 Error: 2: No such file or directory
Additional information: 3
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: '/oracle1/oradata/voipdb/system01.dbf'
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: '/oracle1/oradata/voipdb/system01.dbf'
what shall i do next

Standby redolog files

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