Redologs in RAC

Dear all,
We are running RAC 10.2.0.4 on Solaris 5.10
This is highly transactional DB. The DBA Stating this as the reason, he had created 9 redolog groups on instance 1 and 6 redologs groups on instance 2. recently we had a problem
MED1 - Can not allocate log, archival required
Tue Aug 18 09:46:05 2009
Thread 1 cannot allocate new log, sequence 53164
All online logs needed archiving
So he increased number of redol groups and number of log_archive_processes=10
Can we have different number of redo groups with same sizes in this RAC Instance ?
Please advise
Kai

>
We are running RAC 10.2.0.4 on Solaris 5.10
This is highly transactional DB. The DBA Stating this as the reason, he had created 9 redolog groups on instance 1 and 6 redologs groups on instance 2. recently we had a problem
MED1 - Can not allocate log, archival required
Tue Aug 18 09:46:05 2009
Thread 1 cannot allocate new log, sequence 53164
All online logs needed archiving
So he increased number of redol groups and number of log_archive_processes=10
Can we have different number of redo groups with same sizes in this RAC Instance ?
>
Although it is common to have the same number of redolog groups for each instance, that is not necessarily so. If really the first instance has much higher peak activity than the second, it may be a valid approach to increase the number of redolog groups for that instance. With a higher number of log groups, the chances are better that the archivers managed to archive the log groups for the to be current group if the peak load is over.
In order to make that approach successful, there has to be a phase of less activity on the first instance, though. If there is a constant high load, it won't help.
Kind regards
Uwe
http://uhesse.wordpress.com

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854393 wrote:
Thanks Shivanandha,
(maximum number of logfiles for each thread + 1) * maximum number of threads
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Hope This helps.

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Manish Nashikkar wrote:
Hi Guys,
Setup: Two Node 11gR2 (11.2.0.1) RAC on RHEL 5.4
Existing disks are from Old SAN & New Disks are from New SAN.
Can I move all datafiles (+DATA), controlfiles (+CTRL), redolog (+REDO) on new ASM Disks by adding disks in is same Diskgroup & dropping older disks from existing Diskgroup taking advantage of ASM Re-balancing Feature.
1) add required disks in the DATA Diskgroups,
ALTER DISKGROUP DATA ADD DISK
'/dev/oracleasm/disks/NEWDATA3' NAME NEWDATA_0003,
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'/dev/oracleasm/disks/NEWDATA5' NAME NEWDATA_0005
REBALANCE POWER 11;
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ALTER DISKGROUP DATA DROP DISK
NEWDATA_0000,
NEWDATA_0001
REBALANCE POWER 11;
Check rebalance status from v$ASM_OPERATION.
3) Do it same for Redo log groups & Controlfile Diskgroups.
I hope, I could do this Activity, even if database is Up. is there possibility of Database block Corruption ??? (or is it necessary to perform above steps when database is down)
Would be appreciated, your quick responses on the same.
It's an urgent requirement. Thanks.
Regards,
Manish
Hi Manish,
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Hi,
I have small doubt regarding redolog corruption/deletion in RAC Instance:
OS: RHEL 4.5
Oracle: 10.2.0.1
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1. When a checkpoint is issued.
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Niall Litchfield wrote:
El DBA wrote:
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Niall Litchfield
http://www.orawin.info/
By the way, it seems Robert has been pretty helpful, it's polite to give him some points dude. And since this is your thread, not mine, give him a "helpful" from me too :p
El DBA
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Niall Litchfield
http://www.orawin.info/

How to add members in REDO group in RAC

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I need to know the syntax to add members in redolog group in RAC database. Currently i have 4 groups (2 belonging to each thread) and one member in each group. I want to multiplex.
Thanks in advance

Check out:
http://www.lc.leidenuniv.nl/awcourse/oracle/rac.920/a96600/mancrea.htm

Add a disk to RAC

Hello,
I have a RAC database with 2 nodes and a cluster.
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Archive Generation in RAC environment.

Gems,
I have one doubt it was not able to solve from my mind i.e.
As per my knowledge,
1) Every instance has its own thread so Thread is instance specific. My questions are, How the SCN will be maintained in ARCHIVES? will thread 1 & thread2 contains the same SCN?
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run
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Hi,
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I would first say if you are planning to create the standby for report it is for off loading the report from production database. If you create the reporting instance on the same hardware you would still e sharing if the primary service is active on the node that the reporting instance is running on. You would also be sharing the storage unless you separate the storage. If this is SAN storage you would be using the same HBA card.
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1. Is it good and recommended practice to place the redologs on ASM?
or
2. RAID 10 is the best for redologs in terms of performance?
Thanks, Suvesh

Performance generally depends on your configuration, for instance, how many devices are involved during a read and write operation.
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Best practice online redologs redundant

Oracle dbs on Unix without ASM
Few DBs have only single oracle filesystem available on unix box & have only one online redolog file available, wondering what would be the best practice to redundant them?
I know if i have multiple oracle filesystems , i can spread them there. but with only one filesystem, i can create one more redolog and put on the same filesystem.

All right here is my researchwork on this topic, make me right if i miss something, its not RAC, just single instance dbs.
Advantages
Oracle recommends that you mutliplex the online redo log files, store members on separate disk drives, Even if all
copies of the redo log are on the same disk, the redundancy can help protect against I/O errors, file corruption, and
so on.
Disadvantages
Multiplex redo log files. the database must increase the amount of I/O that it performs. Depending on your
configuration, this may impact overall database performance.
Each member in a group must be exactly the same size.
select GROUP#, MEMBER from v$logfile;
select GROUP#, MEMBERS, STATUS , BYTES from v$log;
ALTER DATABASE ADD LOGFILE MEMBER '/oracle/dbs/log2b.rdo' TO GROUP 2;
alter system switch logfile; (few times to make sure all ok)
Backout plan
alter database drop logfile member '/wmbrktst/oradata/wmbrktst/redo01.log';

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Sorry if this info is a bit vague, im not an Oracle expert! :-)
thanks,
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Hi,
1.) The calculation for Standby RedoLogs is:
(Max Number of Logfiles per thread (Instance) +1) * Max Number of Threads (Instances))
So if you have 4 Redo Log Groups on your primary (which is 2 Redo Log Groups per Instance), then it ends up:
(2 +1) * 2 = 6
So actually you will only need 6 standby redo logs, not 8. But 2 more don't harm.
Your primary will need exactly the same number (6 or in your case 8). Which will be 3 per thread/instance or in your case 4.
2.) The SID List in the listener.ora is a listing of SIDs the Listener is listening on. It is not the listener name.
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Last but not least the SID entries for dataguard have to use DGMGRL not dgmgrl.
3.) Here is the whitepaper you are looking for:
www.oracle.com/goto/maa
Also for client failover best practices.
(Here the direct link to the RAC whitepaper):
http://www.oracle.com/technetwork/database/features/availability/maa-wp-10g-racprimarysingleinstance-131970.pdf
However since this is 10g you should combine this with the 11g RAC standy paper (e.g. SCAN Listener setup).
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Configuring data guard: how many standby redolog do I need?

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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'
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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

Redologs in RAC

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