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

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At the time of copying online redologs to STANDBY site.....

hai..
At the time of configureing dataguard manually(without rman) do i need to copy the online redologs to standby site along with *.dbf files and standby controlfile after clena shutdown? bcaz some procdeures guide me to copy all files with online redolog files to the stanndby environment.but some procedures guide me to only copy the *.dbf files to the standby environment along with init.ora,standby controlfile from the primary site.whcih one is correct? and which one is better?
please guide me.

What is better is to use RMAN.
Why violate "best practice" guidelines.
RMAN knows what to copy and does it correctly.
Hint: If you don't copy the online redologs ... how will they be created? Magic rarely works.

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

Database recovery (online redolog ?)

hi all,
Been awhile since i touch on oracle db, i have been reading around and the emphasis for recovery is always on the backup and archivelog, but i think its wrong.
can i check ->
q1) for full database recovery, do i need the online redo log as well ?
q2) if the answer to q1) is yes, how do i duplicate online redo log to standby site ? (i don't think rsync will work as it cannot sure consistency in the redolog)
will oracle dataguard sync online redolog as well ?
q3) for archivelog, beside manual rsyncing, LOG_ARCHIVE_DEST_2 = 'SERVICE=standby1'
do i need the enterprise edition for the above ?
Regards,
Alan

q1) For a complete recovery, yes you need online redolog as well. Without online redolog,its still considered incomplete recovery since u lose data resides in online redolog
q2) You no need to synch online redo log manually. Once the backup is restored to the DR dataguard site and MRP process initiated, Oracle will synch online redolog/archivelog automatically based on protection mode specified
q3) Oracle dataguard applies to Enterprise Edition only. Without Enterprise Edition, we can configure log shipping (manual way).
Regards,
Ilan

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';

Size of an online redolog file member

How to reduce the size of an online redolog file member

You can add a new logfile, then switch logfile, then drop the old one.
You cannot have different members sizes in the same group.
Regards
Laurent Schneider
OCM-DBA

Resize online redolog files, make RMAN obsolute backups as usable

Dear Guru's,
I have following doubts, please clarify me on the same. thanks in advance
1. why can not we resize online redolog files instead of re-creating the same with large size and remove the older onces.
2. How can we make RMAN obsolute backups as usable ?
Thanks.

vasuoracledba wrote:
Hi Aman,
Thanks for replay...
Regarding RMAN, plz look into below issue.
I configured RMAN backup recovery window of 15 days. after 15 days the backupsets which were older then 15 days are obsolute. now i have to restore the backup of 15 days older(obsolute backupsets) backupsets to the database. but when i do restore it defaulty takes latest backupsets other then obsolute onces.
how do i restore older(obsolute backupsets) backupsets to the database?
If i used the CHANGE cmd, how to do that.
RMAN> change backupset tag weekly_backup_20052013_02:45 _______________
do i make latest backupsets unavaliable to restore the older once....
RMAN> change backupset tag weekly_backup_20062013_02:00;
Thanks in advance...........
Obsolete backups are always usable, until you delete them with DELETE OBSOLETE.
If you want to restore from a backup other than the latest, use an until clause:
run {set until time = 'sysdate - 15';
restore database;}

Online Redologs file

Hi,
Aftr oracle patch upgradation my oracle 10g Database online redolog files are genrated with ROOT:SYSTEm(group&OWNER) inplace of ora<SID>
Please let me know the possible reson and solution of it.
Thanks
Presu

Hi,
Its looking like permission issues (s-bit issue) with database executables like BRARCHIVE, BRBACKUP and others.
Please read the following SAP Notes and do the needful.
[ Note 113747 - Permissions for DBA tools BR*Tools and SAPDBA|https://service.sap.com/sap/support/notes/113747]
[Note 651351 - BR tools on UNIX: Error due to executable permissions|https://service.sap.com/sap/support/notes/651351]
Regards,
Bhavik G. Shroff

Online Redolog file/group creation date

How to check Online Redolog group/file creation date.

Mano wrote:
How to check Online Redolog group/file creation date.Given that the online redo logs are constantly re-used, I'd have to ask what problem do you think will be solved by knowing the creation date . . .
Personally, I can't think of a more useless piece of information, so perhaps you'd get better information if you told us the real problem you are trying to solve.

Change the Online redolog file

Hi Experts,
Please help me.
For SAP Recommondation we want change Online Redolog file.
How can to change Online Redolog file system .
Change minimal size of online redo log file from 20971520 to 63000000
Please explain what is the procedure.
Regards
S.Prasad

review Note 79341 - Checkpoint not complete available at https://service.sap.com/~form/handler?_APP=01100107900000000342&_EVENT=REDIR&_NNUM=79341&_NLANG=E
check for section 3.
HTH

Restore and apply online redologs into different directory

Hi all!
I need to restore oracle db to other directory of another sap system (instance).
I successfully restored control files & datafiles into other directory but oracle not starting.
Probably because there is no necessary online archive redologs.
How can i restore necessary online redologs into different directory and apply them?
Thanks for help

I have some troubles. Maybe /oracle/TSM/sapdata1/system_1/system.data1' really unconssistent?
But i recovered datafiles from tape....
SQL> @/oracle/TSM/saptrace/usertrace/control.sql
Control file created.
SQL> shutdown
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Database mounted.
SQL> recover database using backup controlfile until cancel;
ORA-00279: change 113646088 generated at 05/27/2011 18:04:28 needed for thread
1
ORA-00289: suggestion : /oracle/TSM/oraarch/TSMarch1_3817_598559720.dbf
ORA-00280: change 113646088 for thread 1 is in sequence #3817
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
ORA-00308: cannot open archived log
'/oracle/TSM/oraarch/TSMarch1_3817_598559720.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-01195: online backup of file 1 needs more recovery to be consistent
ORA-01110: data file 1: '/oracle/TSM/sapdata1/system_1/system.data1'
SQL> alter database open resetlogs;
alter database open resetlogs
ERROR at line 1:
ORA-01195: online backup of file 1 needs more recovery to be consistent
ORA-01110: data file 1: '/oracle/TSM/sapdata1/system_1/system.data1'
SQL> shutdown
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Database mounted.
ORA-01589: must use RESETLOGS or NORESETLOGS option for database open
Edited by: Andrey Burakov on Jun 2, 2011 5:04 PM
Edited by: Andrey Burakov on Jun 2, 2011 5:05 PM

Standby db no online redologs

I've created a standby database using RMAN and it works and is applying the archive redo logs automatically.
I re-created the temporary tablespaces.
One thing that is missing is any online redo logs on the standby database.
Should I re-create then manually as I did the temporary tablespaces?

You can always have standby redo logs on standby database.
By the way, what the protection mode of your primary database?
Jaffar

Online Redolog Archiving on Logical Standby Databases!!

Hi,
Can I safely stop archiving on logical standby database? It has been inherited from primary database at the time of creation, but I don't see any reason why to keep it enabled while it's consuming unnecessary disk space on our server!!
Any body can give a valid reason to keep it enabled??
Thanks

hi
u dont need archiving on standby database as standby database reads archive files that come from primary database.its simply wastage of resource.stand by database was created from primary by taking a full backup.and to apply the archive files in case of failure u need atleast 1 backup of stand by database .and i assume u wont go for taking backup of standby database.
just worry about the archives of primary database.
kanchan
OCP ( 9i,10g)

Redolog in standby

Hi Chaps
I know that the redologs are not being used in physical standby database.
So why do I see "CLEARING_CURRENT" or "CLEARING" in their status? and their status changes.
Does that mean that they are used?

Setting the 'CLEARING' status is done for performance reasons (through commands like RMAN DUPLICATE ... FOR STANDBY) , the online are prepared for a faster switchover/failover. But there are not used until such a switch happens,from documentation:
Clearing Online Redo Logs
After creating the standby database, you can clear online redo logs on the standby site to optimize performance by issuing the following statement, where 2 is the number of the log group:
SQL> ALTER DATABASE CLEAR LOGFILE GROUP 2;
This statement optimizes failover to the standby database because it is no longer necessary for the Oracle database server to clear the logs before failover. Clearing involves writing zeros to the entire contents of the redo log and then setting a new header to make the redo log look like it was when it was created.
If you clear the logs manually, the Oracle database server realizes at activation that the logs already have zeros and skips the clearing step. This optimization is important because it can take a long time to write zeros into all of the online logs. If you prefer not to perform this operation during maintenance, the Oracle database server clears the online logs automatically during failover.
Werner

SAP GoLive : File System Response Times and Online Redologs design

Hello,
A SAP Going Live Verification session has just been performed on our SAP Production environnement.
SAP ECC6
Oracle 10.2.0.2
Solaris 10
As usual, we received database configuration instructions, but I'm a little bit skeptical about two of them :
1/
We have been told that our file system read response times "do not meet the standard requirements"
The following datafile has ben considered having a too high average read time per block.
File name -Blocks read - Avg. read time (ms) -Total read time per datafile (ms)
/oracle/PMA/sapdata5/sr3700_10/sr3700.data10 67534 23 1553282
I'm surprised that an average read time of 23ms is considered a high value. What are exactly those "standard requirements" ?
2/
We have been asked to increase the size of the online redo logs which are already quite large (54Mb).
Actually we have BW loading that generates "Chekpoint not comlete" message every night.
I've read in sap note 79341 that :
"The disadvantage of big redo log files is the lower checkpoint frequency and the longer time Oracle needs for an instance recovery."
Frankly, I have problems undertanding this sentence.
Frequent checkpoints means more redo log file switches, means more archive redo log files generated. right ?
But how is it that frequent chekpoints should decrease the time necessary for recovery ?
Thank you.
Any useful help would be appreciated.

Hello
>> I'm surprised that an average read time of 23ms is considered a high value. What are exactly those "standard requirements" ?
The recommended ("standard") values are published at the end of sapnote #322896.
23 ms seems really a little bit high to me - for example we have round about 4 to 6 ms on our productive system (with SAN storage).
>> Frequent checkpoints means more redo log file switches, means more archive redo log files generated. right?
Correct.
>> But how is it that frequent chekpoints should decrease the time necessary for recovery ?
A checkpoint is occured on every logswitch (of the online redologfiles). On a checkpoint event the following 3 things are happening in an oracle database:
Every dirty block in the buffer cache is written down to the datafiles
The latest SCN is written (updated) into the datafile header
The latest SCN is also written to the controlfiles
If your redologfiles are larger ... checkpoints are not happening so often and in this case the dirty buffers are not written down to the datafiles (in the case of no free space in the buffer cache is needed). So if your instance crashes you need to apply more redologs to the datafiles to be in a consistent state (roll forward). If you have smaller redologfiles more log switches are occured and so the SCNs in the data file headers (and the corresponding data) are closer to the newest SCN -> ergo the recovery is faster.
But this concept does not really fit the reality because of oracle implements some algorithm to reduce the workload for the DBWR in the case of a checkpoint.
There are also several parameters (depends on the oracle version) which control that a required recovery time is kept. (for example FAST_START_MTTR_TARGET)
Regards
Stefan

Online redolog on standby

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