Log_file_name_convert , db_recovery_area and multiplexed redo logs

Hi, I have a confusion here, need help.
I have multiplexed redo log members on both asm diskgroup DATA, FRA.
My log_file_name_convert='+DATA', '+DATA'
and db_recovery_area ='+FRA'
db_create_online_log_dest_1=+DAT
Are above parameters right?

log_file_name_convert is simply a string replacing function.Its same behaviour like DB_FILE_NAME_CONVERT
So all entries of <first> will be replaced by <second> and the <third> entry will be replaced by the <fourth> and so on.Yes the strings should be in even numbers like 2,4,6,8.. ther should be sequence for the source & destination diskgroup and so on.
So if you would have:
'DATA','REPLACE','FRA','REPFRA'
all occurences of DATA will be replaced with RAPLACE. But this would also mean ORADATAGRAM would be replaced to ORAREPLACEGRAM.If any ORL's / SRL's are created in DATA in source, by mentioning LOG_FILE_NAME_CONVERT those will be created to the connected proceeding string...
Can you point out please where is mistake in my previous post?

Similar Messages

Multiplexing Redo Log and maximum protection mode.

Assume that during writing into redo logs the instance crashes. As a result, members of active redo group are not synchronized, some of them had more data. How Oracle will handle this when instance starts? And there can be case when at startup time some members that had more redo before crash, are lost.
Now assume that we have standby database with maximum protection mode. After LGWR has written to local redo logs and before writing to standby redo logs, primary instance crashes. In this case standby site lost last transaction.
Is it correct? Thanks.

Assume that during writing into redo logs the instance crashes. As a result, members of active redo group are not synchronized, some of them had more data. How Oracle will handle this when instance starts? And there can be case when at startup time some members that had more redo before crash, are lost.
Members of a particular group are written concurrently by LGWR, all members of a log group will have same data. If any member of a particular group is lost or not reachable, oracle will read from the available log member during instance recovery.
Multiplexing Redo Log Files
http://docs.oracle.com/cd/B19306_01/server.102/b14231/onlineredo.htm#i1006249
To answer your second question,In this mode no transaction commits on primary unless the redo is also written on atleast one standby database, otherwise primary will go down.
Check below
Maximum Protection
http://docs.oracle.com/cd/B28359_01/server.111/b28294/protection.htm#CHDHFHJI

Multiplexing redo log files

I am using 9i R2 database.
I just want to clear some doubts.
I am having 3 redo log groups with one member each.
Now for mutiplexing redo log files
i want to add one one member to each group so
that each group will have 2 members in some different path.
my current path of log member are
/oracle/files/a1.log (group 1)
/oracle/files/b1.log (group 2)
/oracle/files/c1.log (group 3)
I want to add
/oracle/sysfiles/a2.log (group 1)
/oracle/sysfiles/b2.log (group 2)
/oracle/sysfiles/c2.log (group 3)
A--So is there any need to take database in any mode (nomunt,mount) or i can do it while
database is open ?
I will issue
ALTER DATABASE ADD LOGFILE MEMBER /oracle/sysfiles/a2.log TO GROUP 1 ;
First in inactive group,then
alter system switch logfile; (To make 2 group inactive....and then 3)
B-- All memebers in a redolog group must be of same size? if i am having
100 M.B. of one member(a1.log) is there no need to specify size while adding new member(a2.log)?
Can some one validate and correct my steps or suggest me regarding this?

Hi,
All the solutions are in oracle documentaiton.
See, Members of the same multiplexed redo log group must be the same size (that all member in with in the group ) and Members of different groups can have different sizes. If the same of Files are different resultant would be the with Checkpoints. Since you can not gurantee that Checkpoints will occur at regular internals (Log switch with respect log members). Better to follow the Rules of traffic similarly follow the instrcutions of ORACLE Documentation.. :-)
- Pavan Kumar N

Multiplexing Redo Log Files question

If you are running RAC on ASM on a RAID system, is this required? We are using an HP autoraid which mirrors at the block level and in the documentation about Multiplexing Redo Log Files it says that you do it to protect against media failure. The autoraid that we are using gives us multiple levels of redundancy against media failure so I was wondering if Multiplexing would be adding more overhead than is needed. Thanks for your input.

ASM is quite compex and I'm not going to outline all the advantages or reasons for ASM, but under ASM you can drop and add devices to maintain your capacity needs online without loosing data, which you cannot do using RAID, which requires a re-initialize, for example, regardless of redundancy. Please see the documentation. ASM, like pretty much everything Oracle will add complexity and you will have to check your requirements. ASM is however pretty much the standard. If you use external RAID, make sure your storage is not using RAID 5 or 0. Regarding logical errors, you could for example overwrite or delete a file by mistake, in which case file redundancy does not protect you. If you are looking for reasons or ways not to use ASM, I'm sure you will find them, but what's the point?

Why multiplex redo log group ?

Hello,
Why should we multiplex redo log groups if we have only file system which is already mirrored. Is there any one who had an incident when he has only one redo log member per group placed on a mirrored file system but still got corrupted and he felt better to have multiple members even if they reside on the same file system (which is mirrored)
Thanks
Salman

Ansiktet wrote:
EdStevens wrote:
Salman Qureshi wrote:
Hello,
Why should we multiplex redo log groups if we have only file system which is already mirrored. Is there any one who had an incident when he has only one redo log member per group placed on a mirrored file system but still got corrupted and he felt better to have multiple members even if they reside on the same file system (which is mirrored)
Thanks
SalmanThe mirror won't protect you from an SA who deletes '/u01/oradata/redo01.log' because he is running out of space on /u01 and figures its safe to delete a log file.
Or similar types of errors.
The redo and control files are simply too critical to put all your eggs in one basket when planning their protection.:) Thats why you should not use Oracle default .log on redo, instead .dbf or .dbl can be used. THat's why I use the older (pre-10g) default of .rdo for redo logs
However, has this happend anyone for real, that a SA delete Oracle files? Where do you think I came up with the example?
HOw about an SA (or maybe the kind of "fresher" we often see here, Taking a look at a "log" file with notepad?
If he is isnt stupid he should know that Oracle resides on /u01 partion (for example), and should not delete files there without consulting the DBA."should" is the operative word there. There is no accounting for corporate cultures and attitudes.
But end the end, my example was to illustrate that not all problems with redo and control files are mitigated with disk mirroring.

ASM Environment multiplexed redo logs

When we have multi diskgroups like ('+DATA','+FLASH) and configured to multiplexed redologs on asm environment what would be the performance impact while logwriter writing on multiple locations? The diskgroups have different number disks on each diskgroup. Like 100 vs 10 disks on diskgroup.

http://download.oracle.com/docs/cd/B19306_01/server.102/b14231/onlineredo.htm
Multiplexing Redo Log Files help protect against a failure involving the redo log itself.
after you implement, you should check AWR report about waiting.
On ASM, you don't need to make multiple redo files. Just place it (redo file) in good i/o diskgroup (RAID1/0)

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..

The file structure online redo log, archived redo log and standby redo log

I have read some Oracle documentation for file structure and settings in Data Guard environment. But I still have some doubts. What is the best file structure or settings in Oracle 10.2.0.4 on UNIX for a data guard environment with 4 primary databases and 4 physical standby databases. Based on Oracle documents, there are 3 redo logs. They are: online redo logs, archived redo logs and standby redo logs. The basic settings are:
1. Online redo logs --- This redo log must be on Primary database and logical standby database. But it is not necessary to be on physical standby database because physical standby is not open. It doesn't generate redo log. However, if don't set up online redo log on physical standby, when primary failover and switch standby as primary. How can standby perform without online redo logs? In my standby databases, online redo logs have been set up.
2. Archived redo logs --- It is obviously that primary database, logical and physical standby database all need to have this log file being set up. Primary use it to archive log files and ship to standby. Standby use it to receive data from archived log and apply to database.
3. Standby redo logs --- In the document, it says A standby redo log is similar to an online redo log, except that a standby redo log is used to store redo data received from another database. A standby redo log is required if you want to implement: The maximum protection and maximum availability levels of data protection and Real-time apply as well as Cascaded destinations. So it seems that this standby redo log only should be set up on standby database, not on primary database. Am my understanding correct? Because I review current redo log settings on my environment, I have found that Standby redo log directory and files have been set up on both primary and standby databases. I would like to get more information and education from experts. What is the best setting or structure on primary and standby database?

FZheng:
Thanks for your input. It is clear that we need 3 type of redo logs on both databases. You answer my question.
But I have another one. In oracle ducument, it says If you have configured a standby redo log on one or more standby databases in the configuration, ensure the size of the current standby redo log file on each standby database exactly matches the size of the current online redo log file on the primary database. It says: At log switch time, if there are no available standby redo log files that match the size of the new current online redo log file on the primary database. The primary database will shut down
My current one data gurard envirnment setting is: On primary DB, online redo log group size is 512M and standby redo log group size is 500M. On the standby DB, online redo log group size is 500M and standby redo log group size is 750M.
This was setup by someone I don't know. Is this setting OK? or I should change Standby Redo Log on standby DB to 512M to exactly meatch with redo log size on primary?
Edited by: 853153 on Jun 22, 2011 9:42 AM

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

How could I find specified date of REDO log and archive REDO log ?

we use Oracle11gr2 on win2008R2.
1
How could I find specified date of REDO log(2013/10/17,etc) and archive REDO log ?
2
What is the format of archive REDO log.? (zipped file ?)

user12075536123 wrote:
1)
select * from v$archived_log;
select * from v$log_history;
but there is a possibility there is no old data
below contains no filename column
SQL> desc v$log_history
Name                                      Null?    Type
RECID                                              NUMBER
STAMP                                              NUMBER
THREAD#                                            NUMBER
SEQUENCE#                                          NUMBER
FIRST_CHANGE#                                      NUMBER
FIRST_TIME                                         DATE
NEXT_CHANGE#                                       NUMBER
RESETLOGS_CHANGE#                                  NUMBER
RESETLOGS_TIME                                     DATE
there is NO data when archive mode is disabled

What is the difference between undo tablespace and online redo log files.

what is the difference between undo tablespace and online redo log files. I am confused
as per my knowledge undo tablespace is used to store the undo information when a table is being updated so that, just incase we need to rollback a transaction we know what was present in the table earlier.
when a transaction fails the SMON performs the rollback of the data.
This undo data is stored in the undo tablespace and read consistency if any is enforced.
is my understanding till here correct?
Now, can this undo data/before image not be stored in the redo log buffer and online redolog files?
can redo-log files not store this information?
in fact, is it that when undo tablespaces exist in a database, the undo data/before image is stored in both the undo tablespace and also the redo log files?
kindly clarify my doubt.
thank you.

This question has been asked many times before. The answer is always the same.
Yes, redo contains the before image of data (and the after-image). Therefore, it **COULD** be used to roll back a transaction.
BUT... Redo is written sequentially. Using it to rollback your transaction would involve reading through all the redo written by maybe thousands of other people. It would be painfully slow.
Your transaction is, however, directly linked to just the UNDO that it generates (which is JUST the before image of the data). So, your undo is your undo and doesn't share space with anyone else's undo. Therefore, using it to roll back YOUR transaction is fast.
The fact that undo is only the before image of the data also makes it faster than wading through a sea of before and AFTER images as you'd find in redo. About twice as fast, in fact, since there's half the data. Roughly.
Redo also gets written and flushed to disk whenever there's a commit, 3 seconds are up or too much (1MB, actually) redo gets generated between flushes caused by other factors. Your redo gets flushed when those things happen, even if you haven't actually committed your transaction. And redo logs recycle themselves, meaning that your redo -even if your transaction hasn't been committed yet- can be over-written by later transactions. Try rolling back when that's happened, if redo was the source of your rollback data!
Undo, however, cannot be over-written if the transaction has not been committed. Ever. If you don't commit for three years, there will be three years' undo stored in your database (assuming you had the space, of course!).
I could go on, but that will do. Redo is there fore RECOVERY, after catastrophe. Undo is there for read-consistency (and the occasional change of mind). Two different functions. Two different mechanisms. Each one highly tuned to doing what it does, why it does it, most efficiently and effectively.

Multiplex Redo Logs and Control File

I am wanting to setup an existing Oracle Express 10g instance to multiplex the redo log files and the control file.
Instance is using Oracle-Managed Files and the Flash Recovery Area.
With these options being used what are the steps required to setup multiplexing?
I tried setting the DB_CREATE_ONLINE_LOG_DEST_1 and DB_CREATE_ONLINE_LOG_DEST_2 parameters but this doesn't appear to have worked (I even bounced the db instance).
BTW, the DB_CREATE_FILE_DEST is set to null and the DB_RECOVERY_FILE_DEST is set to the flash recovery area.
Any help is much appreciated.
Regards, Sheila

Thanks for this. My instance originally had two log groups so I've added a new member to each group into the same flash recovery area directory, but have assigned a name. Is this why when I query v$logfile the is_recovery_dest_file is set to NO? Is it ok to assign a name & directory and if not, how do you add a new memeber and allow Oracle-Managed files to name them?
Also, how can I check that the multiplexing is working (ie the database is writing to both sets of files)?
Thanks again.

Multiplexing redo logs and control files to a separate diskgroup

General question this one...
I've been using ASM for a few years now and have always installed a new system with 3 diskgroups
+DATA - for datafiles, control files, redo logs
+FRA - for achive logs, flash recovery. RMAN backup
Those I guess are the standards, but I've always created an extra (very small) diskgroup, called +ONLINE where I keep multiplexed copies of the redo logs and control files.
My reasoning behind this is that if there are any issues with the +DATA diskgroup, the redo logs and control files can still be accessed.
In the olden days (all those 5 years ago!), on local storage, this was important, but is it still important now? With all the striping and mirroring going on (both at ASM and RAID level), am I just being overtly paranoid? Does this additional +ONLINE diskgroup actually hamper performance? (with dual write overheads that are not necessary)
Thoughts?

Some of the decision will probably depend on your specific environment's data activity, volume, and throughput.
Something to remember is that redo logs are sequential write, which benefit from a lower RAID overhead (RAID-10, 2 writes per IOP vs RAID-5, 4 writes per IOP). RAID-10 is often not cost-effective for the data portion of a database. If your database is OLTP with a high volume of random reads/writes, you're potentially hurting redo throughput by creating contention on the disks sharing data and redo. Again, that depends entirely on what you're seeing in terms of wait events. A low volume database would probably not experience any noticeable degraded performance.
In my environment, I have RAID-5 and RAID-10 available, and since the RAID-10 requirement from a capacity perspective for redo is very low, it makes sense to create 2 diskgroups for online redo, separate from DATA, and separate from each other. This way, we don't need to be concerned with DATA transactions impacting REDO performance, and vice versa, and we still maintain redo redundancy.
In my opinion, you can't be too paranoid. :)
Good luck!
K

Hoping for a quick response : EXP and Archived REDO log files

I apologize in advance if this question has been asked and answered 100 times. I admit I didn't search, I don't have time. I'm leaving on vacation tomorrow, and I need to know if I'm correct about something to do with backup / restore.
we have 10g R2 running a single instance on a single server. The application vendor has "embedded" oracle with their application. The vendor's backup is a batch file using EXP - thus:
exp system/xpwdxx@db full=y file=D:\Orant\admin\db\EXP\db_full.dmp log=D:\Orant\admin\db\EXP\db_full.txt direct=y compress=y
This command is executed nightly at midnight. The files are then backed up by our nightly backup to offsite storage media.
Te database is running in autoarchive mode. The problem is, the archived redo files filled the drive they were being stored on, and it is the drive the database is on. I used OS commands to move 136G of archived redo logs onto other storage media to free the drive.
My question: Since the EXP runs at midnight, when there is likely NO activity, do I need to run in AutoArchive Mode? From what I have read, you cannot even apply archived redo log files to this type of backup strategy (IMP) Is that true? We are ok losing changes since our last EXP. I have read a lot of stuff about restoring consistent vs. inconsistent, and just need to know: If my disk fails, and I have to start with a clean install of Oracle and nothing else, can I IMP this EXP and get back up and running as of the last EXP? Or do I need the autoarchived redo log files back to July 2009 (136G of them).
Hoping for a quick response
Best Regards, and thanks in advance
Bruce Davis

Bruce Davis wrote:
Amardeep Sidhu
Thank you for your quick reply. I am reading in the other responses that since I am using EXP without consistent=y, I might not even have a backup. The application vendor said that with this dmp file they can restore us to the most recent backup. I don't really care for this strategy as it is untested. I asked them to verify that they could restore us and they said they tested the dmp file and it was OK.
Thank you for taking the time to reply.
Best Regards
BruceThe dump file is probably ok in the sense it is not corrupted and can be used in an imp operation. That doesn't mean the data in it is transactionally consistent. And to use it at all, you have to have a database up and running. If the database is physically corrupted, you'll have to rebuild a new database from scratch before you can even think about using your dmp file.
Vendors never understand databases. I once had a vendor tell me that Oracle's performance would be intolerable if there were more than 5 concurrent connections. Well, maybe in HIS product ..... Discussions terminated quickly after he made that statement.

Resizing online and standby redo log in dataguard setup.

In 10gr2 dataguard i would like to increase redo logsize from 50M to 100M.
on primary
standby_file_management=manual
added online redo groups with 100M
log switched
drop old one and readded with 100m
deleted log added in step2.
same for standby redo logs.
On standby
was able to resize standby redo logs.
but cannot resize online redologs status is clearing or clearing_current.
please comment. thanks.

I assume you just had to wait until the Primary switched out of that online log so it became inactive at the standby as well? We track where the Primary is by marking the online redo log files at the standby as clearing_current so you can tell where the primary was at any given moment.
Make sure you create new standby redo log files at the Primary and Standby to match the new online redo log file size.
Larry

Log_file_name_convert , db_recovery_area and multiplexed redo logs

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