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

Similar Messages

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

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 redologs

Hi
I created standby redologs and change lgwr async mode. (max performance)
How can I know wheter the standby redologs are used or not?
I want to make sure that db is using standby redologs rather than archive transfer..

Hi..
How can I know wheter the standby redologs are used or not?You can verify using the below query on the standby database:-
SELECT GROUP#,THREAD#,SEQUENCE#,ARCHIVED,STATUS FROM V$STANDBY_LOG;
For V$standby_log refer to [http://download.oracle.com/docs/cd/B14117_01/server.101/b10755/dynviews_2115.htm]
HTH
Anand

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)';

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/

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

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 redolog usage

Hi,
how can we confirm whether standby redologs are using by DG.

Hi,
SQL> select GROUP#,STATUS from v$standby_log;
GROUP# STATUS
4 ACTIVE
5 ACTIVE
6 UNASSIGNED
7 UNASSIGNED
8 UNASSIGNED
9 UNASSIGNED
10 UNASSIGNED
7 rows selected.
If all the standby logs are in UNASSIGNED state then standby logs are not used.
Regards,
S.K.

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

Standby Redolog Creation for Physical standby

I want to migrate my primary database from one server X to standby database which i want to create on other server Y. once Primary and standby will get SYNC , i will do Fail over to make standby as primary and divert current application on standby considering as full functional Primary.
Is it mandatory to create SRL ( Standby redo log)? or I can create physical standby without SRL? If Yes, on which side (primary or standby) i need to create SRL?
Appreciate your help..

Hello,
Now, My standby database has configured. Since i had restore and recover standby database from standby controlfile instead of RMAN Duplicate. I had done following step:
ON standby side:
$rman target /
RMAN> restore standby controlfile from '/app/oracle/standbyctl.ctl'
RMAN> sql 'alter database mount standby database';
RMAN> restore database;
RMAN> list backup of archive log all;
RMAN> RMAN> recover database until sequence 1670;
SQL> alter database recover managed standby database disconnect from session;
• On Primary:
SQL> alter system set log_archive_dest_state_2=ENABLE;
• On Standby:
SQL> select sequence#,applied from v$archived_log order by sequence#;
I am at this stage now. My primary and standby database in synchronization. As per my first thread above, we will have planned outage to move application to standby database and make it full functional primary database. once application will move on new server( standby database). we will not use current primary database anymore.
what are the procedure i need to do on primary side and standby side when migrate application on new server.? rightnow my standby database in MOUNT mode and archive log is shipping from primary to standby. we have no dataguard broker configuration. i need to do it manually using SQL command.

Standby database online redologs

1-)
I know that online redologs are not being used in physical standby database.
Suppose I created a physical standby database with standby redologs.
As far as I know online redologs are not used in standby database,(standby redologs are used)
However, when I check the status of the online redologs in standby database I see that:
"CLEARING_CURRENT" or "CLEARING".
Their status is also changing once log switch occurs in production.
Whats the reason for this and why does this status always change, if standby online redologs are not used, their status
should not change.
2-)
What would happen if I delete the online redolog of the standby database from the operating system?
Does the status again show: clearing,clearing current?

Standby online logs are not used, but they have status CLEARING in preparation for a possible switchover/failover. So they are ready to become very fast active online logs.
I would never delete any database files on OS level, although the standby online logs are not needed when the database runs in standby role, Oracle will complain about their missing. At least when you restart the standby.
Werner

Online redolog on standby

Hello
I know that standby redologs are used in standby database, Does oracle also uses online redologs in standby database? I notice that the status of online redologs changed in standby database
select group#, bytes, status from v$log;
1 10485760 UNUSED
3 10485760 CLEARING_CURRENT
2 10485760 UNUSED

hi..
me too just noticed this...
from my standby
SQL> /
    GROUP#      BYTES STATUS
         3 314572800 CLEARING_CURRENT
         4 314572800 CLEARING
         5 314572800 CLEARING
         6 314572800 CLEARING
         7 314572800 CLEARING
         8 314572800 CLEARING
         9 314572800 CLEARING_CURRENT
        10 314572800 CLEARING
        11 314572800 CLEARING
        12 314572800 CLEARING
10 rows selected.
from my primary
SQL> /
    GROUP#            BYTES STATUS
         3      314,572,800 CURRENT
         4      314,572,800 INACTIVE
         5      314,572,800 INACTIVE
         6      314,572,800 INACTIVE
         7      314,572,800 INACTIVE
         8      314,572,800 ACTIVE
         9      314,572,800 CURRENT
        10      314,572,800 INACTIVE
        11      314,572,800 INACTIVE
        12      314,572,800 INACTIVEGuess in standby, it uses the primary redo logs too and clears it..
thanks,
baskar.l

Conceptual Question-Standby Database

Hi all,
I was just going through this documentation
http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/log_apply.htm
In the beginning it says
"Log apply services automatically apply redo to standby databases to maintain synchronization with the primary database and allow transactionally consistent access to the data"
I want to know How does process takes redo log and apply to datafile?What is basically happening inside?
Cheers,
Neerav

Dear Neerav999,
If i would know your Oracle database version, i could give you a more detailed explanation but i will give it anyway;
There are options that you can use for the Oracle Data Guard. Data Guard is used for replicating the primary database to the standby database via the archivelogs and/or with the redologs. You may not have a standby redolog for maximized performance protection level and it is not mandatory however you need to have standby redos for maximized availiability and protection, protection levels of the Oracle database.
Starting from 11g, you can able to cancel the recovery process on standby site and open the standby database read only than (magic goes here) you can start the media recovery! The command list as follow for 11g;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL --> This command will cancel the MRP0 process and will stop the continuous media recovery
ALTER DATABASE OPEN READ ONLY
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE [USING CURRENT LOG FILE] DISCONNECT FROM SESSION;
--> Above command will start the media recovery process ON THE READ ONLY DATABASE!You can give it a try that one by creating a dummy table on primary and wait for one or two log switches and check back the standby database. You are going to see the table has been also created there.
So answer to your eternal question! :)
MRP process is there to fetch and request the archivelogs from the primary site. This process can be started with the below command;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;You may have a simple test of cource. Cancel the MRP process and switch some logfiles on primary site. Than rerun above command to restart the MRP process and check v$dataguard_status fixed view. You will see that MRP is going to try to fetch the missing archivelog files and will try to close down the gap between the primary and the standby database. Here let me show you another 11g feature of Data Guard.
On 11g you can compress the redologs! What do you need to compress it? There is maybe the most threatning problem of the Data Guard is the connection itself. It should be fast and reliable. Otherwise the MRP process will fall behind and if you are running on maximum performance mode, it will also decrease the performance of the primary database and will hardly close the gap. You 11g Data Guard does is it compresses the log files in the fetching period. If its done with fetching and closed the gap than the normal transmission without the compression will continue to operate. Here is an example of redo compression parameter;
alter system set log_archive_dest_n = 'service= ORCLSTBY
LGWR ASYNC valid_for=(ONLINE_LOGFILES,PRIMARY_ROLE)
db_unique_name=ORCLSTBY compression=enable'I have checked the link that you have given and its Oracle 10g but i have just written it to understand some real factors between the 10g Data Guard and the 11g Data Guard. There are also other changes but if you can go to the 11g New Features site you will see Arup Nanda's posts about it.
If you are to use the standby redologs and it is called "Real Time Apply" and you can see it on v$dataguard_status fixed view. Here is the information from the online documentation;
6.2.1 Using Real-Time Apply to Apply Redo Data Immediately
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.
Use the ALTER DATABASE statement to enable the real-time apply feature, as follows:
    *For physical standby databases, issue the ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE statement.
    *For logical standby databases, issue the ALTER DATABASE START LOGICAL STANDBY APPLY IMMEDIATE statement.
Standby redo log files are required to use real-time apply.Here is a fixed view that you may see the processes;
http://download.oracle.com/docs/cd/B19306_01/server.102/b14237/dynviews_1169.htm#REFRN30144
PROCESS      VARCHAR2(9)      Type of process whose information is being reported:
    *RFS - Remote file server
    *MRP0 - Detached recovery server process
    *MR(fg) - Foreground recovery session
    *ARCH - Archiver process
    *FGRD
    *LGWR
    *RFS(FAL)
    *RFS(NEXP)
    *LNS network server processAll above indications are most verbose and your answer to your question resides here but you need to read it carefully to understand how Oracle applies log files.
http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/manage_ps.htm#i1009613
Regards.
Ogan

Standby redologs mandatory

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