Groups and Member in Redo Log

Hi,
I would like to the defination and the functionality of Groups and Member in a Redo log file and also the distinction between them
Thks

Dear J.C.,
The redo logs are files that the Oracle server uses to commit or rollback the transactions applied by the users.
Redo Log files (minimum of two files) record all changes made to the database, hence ensuring that no data is lost in the event of a failure. In case of an instance failure, when the database is next started up, the Oracle server is automatically able to roll forward the transactions that were not applied when the database crashed and roll back the uncommitted transactions from the rollback segments. Hence the database recovers automatically to a consistent state that existed prior to the crash.
A set of Redo Log files is called a Redo Log Group. Multiple copies (mirroring) of the Redo Log Files are used so as to protect the Redo Log Files from corruption / damage. Each Redo Log File in a Redo Log Group (called Redo Log Member) has essentially the same information, so if one is destroyed, another copy of that file is available for the Oracle server to use.
Finally, the term Redo Log is used interchangeably with Redo Log Group.
Ciao!

Similar Messages

Delete old and unused Archived Redo Log Files

Hello forum!
My db was in ARCHIVELOG mode and It created 9GB of archived redo log files.
Now I put the db in NOARCHIVELOG mode, can I delete all the ARLF? am I sure that the DB never need those files in the future?
If yes, how can I delete them? I will use 'del' operative system command?
In addition, I found this command:
SQL>alter database open resetlogs;
is it useful for my purpose?
thank you!

You are safe to remove those archivelog files if you altered your database to no archive log mode. Just remove them from OS level
Please bear in mind that database in no archivelog mode will lost data in the event of disaster.
SQL>alter database open resetlogs;Doesn't help in your situation, it's use to bring up database after incomplete recovery.

AlwaysOn Availability groups and unable to backup LOG files

Hi,
I have an issue where we are using AlwaysOn availability groups, however my transaction log backup jobs are not working for any databases that are part of the groups. Databases which are standalone backup fine. I've tried using the builtin maintenance
plans as well as the 'maintenance script' from Ola Hallengren which is my preference.
All the jobs are reporting success even though nothing is bring written to disk, the jobs complete within a few seconds.
If I backup the log files individually myself they work fine. After
going a bit of Googling this appears to have been a known issue that was fixed in CU7, unfortunately I'm running CU9 and still have the issue.
I've tried changing the backup preference to any, as well as primary or secondary only to no avail.
I'm using SQL Server SP1 CU9, 2 nodes in the group. Anyone have any suggestions?
Marcus

Hi,
I understand that you have tried every options in Backup Preferences. I still suggest you enable the “For availability database. Ignore Replica Priority for Backup and Backup on Primary Settings” when you define the maintenance plan and check how it works.
This settings is off by default. And the maintenance plan will detect the availability group's AUTOMATED_BACKUP_PREFERENCE setting when deciding to backup a database or log if that database is defined in the group.
'Given that an availability group's default AUTOMATED_BACKUP_PREFERENCE setting is 'SECONDARY, a maintenance plan, defined and running on a SQL Server instance hosting the primary replica, will NOT backup databases defined in the availability group.
Reference:
http://blogs.msdn.com/b/alwaysonpro/archive/2014/01/02/maintenance-plan-does-not-backup-database-or-log-of-database-that-belongs-to-availability-group.aspx
Hope it helps.
Tracy Cai
TechNet Community Support

Abot loss online Redo log group

Hi,
Is there different from recovering between loss CURRENT online redo log group and ACTIVE online redo log group?
Both of them are needed to incomplete recovery, right?

For CURRENT redolog recovery:
startup mount
recover database until cancel;
alter database open resetlogs;
For ACTIVE redolog recovery:
If the database is still running, force a checkpoint by issuing the following command:
alter system checkpoint;
If above was successful and if the lost group has been archived then issue:
alter database clear logfile group <number of the online redo log group>;
And if the lost group has NOT been archived then issue:
alter database clear logfile unarchived group <number of the online redo log group>;
alter database open;
If the database is not running (crashed) then
startup mount
recover database until cancel;
alter database open resetlogs;
Daljit Singh

Adding online redo logs with standby database in place

Hi group,
I have decided to add one new member to my existing redo log groups and an additional redo log group to my primary database.
That change went ok without problems. I assumed that with standby_file_management=auto the equivalent online redo logs are created on the standby database. But this is not the case.
The documentation is unclear about this point and I did not find anything suitable on metalink. The docs suggest to cancel managed recovery on the standy, setting standby_file_management to MANUAL and then adding online logs, quote:
"To add an online redo log, use a SQL statement such as this:
SQL> ALTER DATABASE ADD STANDBY LOGFILE 'prmy3.log' SIZE 100K;"
This however - IMO - adds a new STANDBY redo log to the standby database, what I need is an ONLINE redo log.
Does anybody have some experience to share here?
Facts:
Solaris 8
Oracle 9.2.0.6
Thanks!
Martin

OK, for those who come across the same problem.
You need to create a new standby controlfile, copy it as well as any new online redo log from production to the standby environment.
Once the files are in place, start the standby as normal and open it read only to see if everything is ok:
startup nomount
alter database mount standby database;
alter database open read only
Only when there are no errors in your alert.log you are safe.
Martin

Redo Logs Groups and Members

Hi -
I have a few questions regarding redo log groups and naming conventions I was hoping someone could address or point me to some docs.
I am multiplexing my control file and redo logs across HDDs for an XE installation.
The original logs created at install have the naming form of:
O1_MF_1_462H1GK7_.LOG.
1. What is behind the naming scheme (specifically the _462H1GK7_ section)?
2. Is there a generally recognized naming scheme for adding new group members in XE?
3. I noticed that with any XE install I have done, the redo logs groups default to Group 1 and Group 3, with no Group 2 to be found. Is this normal/required? If not, is it best to add group 2 and then remove group 3? I'm not sure if has much bearing here, but the 10gR2 docs state that skipping group numbers will consume space in the control files.
Thanks in advance for any assistance,
Scott

The odd-looking filename is from using Oracle Managed Files (OMF). You can override the naming scheme or create your own groups and members. Very common to include "redo" in the file name along with group and member identifiers. An example would be:
<path>/redo01a.log
<path>/redo01b.log
<path>/redo02a.log
etc.
You can see group 01 has two members, a and b. Can also include the SID in the file name as well, but that can be identified via the path. 462H1GK7 is a unique identifier generated by Oracle. It has no meaning.
I don't know about XE not creating a group 2. Were there group 2 file(s) left over from a previous install (although the OMF probably would have ignored the existing files)? If creating the files manually, you can use "reuse" to use existing files.

Best way to move redo log from one disk group to another in ASM?

Hi All,
Our db is 10.2.0.3 RAC db. And database servers are window 2003 server.
We need to move more than 50 redo logs (some are regular and some are standby) which are not redundant from one disk group to another. Say we need to move from disk group 1 to 2. Here are the options we are thinking about but not sure which one is the best from easiness and safety prospective.
Thank you very much for your help in advance.
Shirley
Option 1:
1)     shutdown immediate
2)     copy log files from disk group 1 to disk group2 using RMAN (need to research on this)
3)     startup mount
4)     alter database rename file ….
5)     Open database open
6)     delete the redo files from disk group 1 in ASM (how?)
Option 2:
1)     create a set of redo log groups in disk group 2
2)     drop the redo log groups in disk group 1 when they are inactive and have been archived
3)     delete the redo files associated with those dropped groups from disk group 1 (how?) (According to Oracle menu: when you drop the redo log group the operating system files are not deleted and you need to manually delete those files)
Option 3:
1)     create a set of redo members in disk group 2 for each redo log group in disk group 1
2)     drop the redo log memebers in disk group 1
3)     delete the redo files from disk group 1 associated with the dropped members

Absolutely not, they are not even remotely similar concepts.
OMF: Oracle Managed Files. It is an RDMBS feature, no matter what your storage technology is, Oracle will take care of file naming and location, you only have to define the size of a file, and in the case of a tablespace on an OMF DB Configuration you only need to issue a command similar to this:
CREATE TABLESPACE <TSName>; So the OMF environment creates an autoextensible datafile at the predefined location with 100M by default as its initial size.
On ASM it should only be required to specify '+DGroupName' as the datafile or redo log file argument so it can be fully managed by ASM.
EMC. http://www.emc.com No further commens on it.
~ Madrid
http://hrivera99.blogspot.com

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.

Where RFS exactly write redo data ? ( archived redo log or standby redo log ) ?

Good Morning to all ;
I am getting bit confused from oracle official link . REF_LINK : Log Apply Services
Redo data transmitted from the primary database is received by the RFS on the standby system ,
where the RFS process writes the redo data to either archived redo log files or standby redo log files.
In standby site , does rfs write redo data in any one file or both ?
Thanks in advance ..

Hi GTS,
GTS (DBA) wrote:
Primary & standby log file size should be same - this is okay.
1) what are trying to disclose about largest & smallest here ? - You are confusing.
Read: http://docs.oracle.com/cd/E11882_01/server.112/e25608/log_transport.htm#SBYDB4752
"Each standby redo log file must be at least as large as the largest redo log file in the redo log of the redo source database. For administrative ease, Oracle recommends that all redo log files in the redo log at the redo source database and the standby redo log at a redo transport destination be of the same size."
GTS (DBA) wrote:
2) what abt group members ? should be same as primary or need to add some members additionally. ?
Data Guard best practice for performance, is to create one member per each group in standby DB. on standby DB, one member per group is reasonable enough. why? to avoid write penalty; writing to more than one log files at the standby DB.
SCENARIO 1: if in your source primary DB you have 2 log member per group, in standby DB you can have 1 member per group, additionally create an extra group.
primary
standby
Member per group
2
1
Number of log group
4
5
SCENARIO 2: you can also have this scenario 2 but i will not encourage it
primary
standby
Member per group
2
2
Number of log group
4
5
GTS (DBA) wrote:
All standby redo logs of the correct size have not yet been archived.
- at this situation , can we force on standby site ? any possibilities ?
you can not force it , just size your standby redo files correctly and make sure you don not have network failure that will cause redo gap.
hope there is clarity now
Tobi

Question on Redo logs in RAC

DB version:11.2
Platform : Solaris 10
We create RAC DBs manually. Below is a log of the DB creation from Node1 . Instance in Node2 is not yet created (only binary is installed in Node2).
SQL> conn / as sysdba
Connected to an idle instance.
SQL> startup nomount pfile=/u03/oracle/11.2/db_1/dbs/initnehprd1.ora
ORACLE instance started.
Total System Global Area 1252643278 bytes
Fixed Size                  2219208 bytes
Variable Size             771752760 bytes
Database Buffers          469762048 bytes
Redo Buffers                8929280 bytes
SQL> CREATE DATABASE nehprd MAXINSTANCES 8 MAXLOGFILES 16 MAXLOGMEMBERS 4 MAXDATAFILES 1024
2 CHARACTER SET AL32UTF8 NATIONAL CHARACTER SET AL16UTF16
3 DATAFILE '+DG_DATA01/nehprd/nehprd_system01.dbf' SIZE 1000m EXTENT MANAGEMENT LOCAL
4 SYSAUX DATAFILE '+DG_DATA01/nehprd/nehprd_sysaux01.dbf' SIZE 600m
5 DEFAULT TEMPORARY TABLESPACE temp
6 TEMPFILE '+DG_DATA01/nehprd/nehprd_temp01.dbf' SIZE 2000m EXTENT MANAGEMENT LOCAL UNIFORM SIZE 5m
7 UNDO TABLESPACE undotbs11 DATAFILE '+DG_DATA01/nehprd/nehprd_undotbs1101.dbf' SIZE 700m
8 LOGFILE
9          GROUP 1 ('+DG_DATA01/nehprd/nehprd_log01.dbf') SIZE 150m,
10          GROUP 2 ('+DG_DATA01/nehprd/nehprd_log02.dbf') SIZE 150m,
11          GROUP 3 ('+DG_DATA01/nehprd/nehprd_log03.dbf') SIZE 150m
12 /
Database created.
Elapsed: 00:00:18.95
SQL> CREATE UNDO TABLESPACE undotbs12 DATAFILE '+DG_DATA01/nehprd/nehprd_undotbs1201.dbf' SIZE 700m;
Tablespace created.
Elapsed: 00:00:01.30
SQL> ALTER DATABASE ADD LOGFILE thread 2 GROUP 4 '+DG_DATA01/nehprd/nehprd_log04.dbf' SIZE 150m;
Database altered.
Elapsed: 00:00:00.25
SQL> ALTER DATABASE ADD LOGFILE thread 2 GROUP 5 '+DG_DATA01/nehprd/nehprd_log05.dbf' SIZE 150m;
Database altered.
Elapsed: 00:00:00.43
SQL> ALTER DATABASE ADD LOGFILE thread 2 GROUP 6 '+DG_DATA01/nehprd/nehprd_log06.dbf' SIZE 150m;
Database altered.But after the above activity, the following log files are created in the DB.
6 log groups for each Instance and they all are on the same location +DG_DATA01/nehprd !
INST_ID     GROUP# STATUS TYPE             MEMBER                                   IS_
         1          1         ONLINE +DG_DATA01/nehprd/nehprd_log01.dbf             NO
         1          2         ONLINE +DG_DATA01/nehprd/nehprd_log02.dbf             NO
         1          3         ONLINE +DG_DATA01/nehprd/nehprd_log03.dbf             NO
         1          4         ONLINE +DG_DATA01/nehprd/nehprd_log04.dbf             NO
         1          5         ONLINE +DG_DATA01/nehprd/nehprd_log05.dbf             NO
         1          6         ONLINE +DG_DATA01/nehprd/nehprd_log06.dbf             NO
         2          1         ONLINE +DG_DATA01/nehprd/nehprd_log01.dbf             NO
         2          2         ONLINE +DG_DATA01/nehprd/nehprd_log02.dbf             NO
         2          3         ONLINE +DG_DATA01/nehprd/nehprd_log03.dbf             NO
         2          4         ONLINE +DG_DATA01/nehprd/nehprd_log04.dbf             NO
         2          5         ONLINE +DG_DATA01/nehprd/nehprd_log05.dbf             NO
         2          6         ONLINE +DG_DATA01/nehprd/nehprd_log06.dbf             NO How was redo log group 4,5,6 created for thread 1 and how was redo log group 1,2,3 created for thread 2 ?

Hi,
To make things worse, when you query v$logfile , It will show 6 redo logfiles belonging to 6 redo groups for each instance.The fact that it shows all groups of redo does not mean it belongs to that instance. Try to query v$database or v$datafile, this means that database/datafiles belongs to only one instance, of course not.
Isn't this a bit of a bug ?Of course not. It's concept.
To understand it you need understand the difference between instance and database. An database (i.e files) can be opened by many instances.
An Oracle database server consists of a database and at least one database instance (commonly referred to as simply an instance). Because an instance and a database are so closely connected, the term Oracle database is sometimes used to refer to both instance and database. In the strictest sense the terms have the following meanings:
Database
A database is a set of files, located on disk, that store data. These files can exist independently of a database instance.
Database instance
An instance is a set of memory structures that manage database files. The instance consists of a shared memory area, called the system global area (SGA), and a set of background processes. An instance can exist independently of database files.
Database: (v$database)
CONTROLFILE (v$controlfile)
DATAFILE (v$datafile)
ONLINELOG (v$logfile,v$log)
ARCHIVELOG (v$archivelog)
SPFILE
These views above will show the same values in either instance, because if the file (database) is changed it is modified in all instances. That's means you not need use gv$ because the information are the same in all instances, also you not need get info connecting in each instance querying theses v$ because the inf are the same independent of the instance
Instances: (v$instance)
PARAMETERS (v$parameter)
MEMORY STRUCTURE (e.g v$session)
The view v$session will show information about sessions from that instance only. In RAC each instance have you own info about session so you will need query gv$session because it get information about session from others instances.
The fact that each instance assign its own REDO/UNDO not mean they are part of the instances, REDO/UNDO are part of Database. They can be write by assigned instance and read by all instance (just it)
It's not a bug when you query v$datafile, v$logfile, v$controlfile in all instances you will get same result, because it's the DATABASE. (An database (i.e files) can be opened by many instances).
Levi Pereira

Open database if an active online redo log is missing

Hi,
Sorry for the rather long post, but I specified all the steps I performed and couldn't make it shorter :-(
I need an advice on how to open the database if an active online redo log is missing.
For test purposes I intentionally performed a shutdown abort when the redo log group 1 was in active state and then renamed its only member (REDO01.LOG) so that the database couldn't perform crash recovery using it. Then upon startup I obviously got the message:
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: 'H:\ORADATA\TESTDB\REDO01.LOG'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) The system cannot find the file specified.Ok, so I checked the state of the logs:
{noformat}
SQL>SELECT a.GROUP#, first_change#, SEQUENCE#, a.status, SUBSTR(b.MEMBER, 1, 40) MEMBER, b.status mem_status, a.archived
2    FROM v$log a, v$logfile b
3   WHERE a.GROUP# = b.GROUP#
4 ORDER BY a.GROUP#, b.MEMBER;
GROUP# FIRST_CHANGE# SEQUENCE# STATUS           MEMBER                         MEM_STA ARC
     1        592134         29 ACTIVE           H:\ORADATA\TESTDB\REDO01.LOG           YES
     2        592268         30 CURRENT          C:\ORADATA\TESTDB\REDO02.LOG           NO
     3        592129         28 ACTIVE           C:\ORADATA\TESTDB\REDO03.LOG           YES
{noformat}Since opening the database to perform a log switch and thus change the status of the redo log group 1 from ACTIVE to INACTIVE to recreate the member isn't possible, I performed database recovery.
SQL>recover database until cancel;
ORA-00279: change 592129 generated at 02/04/2009 10:31:15 needed for thread 1
ORA-00289: suggestion : C:\ORACLE\PRODUCT\10.2.0\FLASH_RECOVERY_AREA\TESTDB\ARCHIVELOG\2009_02_04\O1_MF_1_28_%U_.ARC
ORA-00280: change 592129 for thread 1 is in sequence #28
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
ORA-00279: change 592134 generated at 02/04/2009 10:31:28 needed for thread 1
ORA-00289: suggestion : C:\ORACLE\PRODUCT\10.2.0\FLASH_RECOVERY_AREA\TESTDB\ARCHIVELOG\2009_02_04\O1_MF_1_29_%U_.ARC
ORA-00280: change 592134 for thread 1 is in sequence #29
ORA-00278: log file 'C:\ORACLE\PRODUCT\10.2.0\FLASH_RECOVERY_AREA\TESTDB\ARCHIVELOG\2009_02_04\O1_MF_1_28_4RLR3JS9_.ARC' no longer needed for this rec
overy
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
'C:\ORACLE\PRODUCT\10.2.0\FLASH_RECOVERY_AREA\TESTDB\ARCHIVELOG\2009_02_04\O1_MF_1_29_4RLR4MF3_.ARC'
ORA-00279: change 592268 generated at 02/04/2009 10:32:03 needed for thread 1
ORA-00289: suggestion : C:\ORACLE\PRODUCT\10.2.0\FLASH_RECOVERY_AREA\TESTDB\ARCHIVELOG\2009_02_04\O1_MF_1_30_%U_.ARC
ORA-00280: change 592268 for thread 1 is in sequence #30
ORA-00278: log file 'C:\ORACLE\PRODUCT\10.2.0\FLASH_RECOVERY_AREA\TESTDB\ARCHIVELOG\2009_02_04\O1_MF_1_29_4RLR4MF3_.ARC' no longer needed for this rec
overy
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
'C:\ORADATA\TESTDB\REDO02.LOG'
Log applied.
Media recovery complete.
SQL>So for log sequence #28 I accepted the proposed archived redo log in the FRA, for sequence #29 (that's the online redo log that is missing!) I manually specified its archived copy, and for sequence #30 I specified the CURRENT online redo log. And as it seems the media recovery was successful.
Next I tried to open the database but again got the error:
SQL>alter database open noresetlogs;
alter database open noresetlogs
ERROR at line 1:
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: 'H:\ORADATA\TESTDB\REDO01.LOG'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) The system cannot find the file specified.
The status of the log groups and its members is exactly as it was in the first query I wrote above, i.e. the redo log group 1 is still ACTIVE, so it's needed for crash recovery (which I had already done manually if I understand correctly how Oracle works!). I also checked if the datafiles are inconsistent (described in metalink doc id 1015544.102):
SQL>SELECT DISTINCT CHECKPOINT_CHANGE#, FUZZY FROM V$DATAFILE_HEADER;
CHECKPOINT_CHANGE# FUZ
            592269 NOSo, everything seems ok as far as datafile consistency is concerned.
My question is: how can I rename/drop/clear/whatever the member of redo log group 1 to open the database?
I tried to rename the log file member, to add another member to it, to open the database with resetlogs, to clear the logfile group 1, but all without success:
1)
SQL>alter database clear logfile group 1;
alter database clear logfile group 1
ERROR at line 1:
ORA-01624: log 1 needed for crash recovery of instance testdb (thread 1)
ORA-00312: online log 1 thread 1: 'H:\ORADATA\TESTDB\REDO01.LOG'
2)
SQL>alter database open resetlogs;
alter database open resetlogs
ERROR at line 1:
ORA-01139: RESETLOGS option only valid after an incomplete database recovery
3)
SQL>alter database rename file 'H:\ORADATA\TESTDB\REDO01.LOG' to 'C:\ORADATA\TESTDB\REDO01.LOG';
alter database rename file 'H:\ORADATA\TESTDB\REDO01.LOG' to 'C:\ORADATA\TESTDB\REDO01.LOG'
ERROR at line 1:
ORA-01511: error in renaming log/data files
ORA-01512: error renaming log file H:\ORADATA\TESTDB\REDO01.LOG - new file C:\ORADATA\TESTDB\REDO01.LOG not found
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) The system cannot find the file specified.
4)
SQL>alter database add logfile member 'C:\ORADATA\TESTDB\REDO01.LOG' to group 1;
alter database add logfile member 'C:\ORADATA\TESTDB\REDO01.LOG' to group 1
ERROR at line 1:
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: 'H:\ORADATA\TESTDB\REDO01.LOG'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) The system cannot find the file specified.Sorry again for the long post and thank you in advance for any suggestion.
Regards,
Jure

You could check if the recovery was complete by (re)creating the controlfile with the resetlogs option.
<CREATE CONTROLFILE REUSE DATABASE define_db_name RESETLOGS NOARCHIVELOG
...>Thanks for the hint. If possible, could you only check if the steps I'm going to perform are ok.
I did an "alter database backup controlfile to trace;" and then extracted the create controlfile definition part. So in essence I should run the following statements:
CREATE CONTROLFILE REUSE DATABASE "TESTDB" RESETLOGS ARCHIVELOG
    MAXLOGFILES 16
    MAXLOGMEMBERS 3
    MAXDATAFILES 100
    MAXINSTANCES 8
    MAXLOGHISTORY 292
LOGFILE
GROUP 1 'C:\ORADATA\TESTDB\REDO01.LOG' SIZE 20M,
GROUP 2 'C:\ORADATA\TESTDB\REDO02.LOG' SIZE 20M,
GROUP 3 'C:\ORADATA\TESTDB\REDO03.LOG' SIZE 20M
-- STANDBY LOGFILE
DATAFILE
'C:\ORACLE\PRODUCT\10.2.0\ORADATA\TESTDB\SYSTEM01.DBF',
'C:\ORACLE\PRODUCT\10.2.0\ORADATA\TESTDB\UNDOTBS01.DBF',
'C:\ORACLE\PRODUCT\10.2.0\ORADATA\TESTDB\SYSAUX01.DBF',
'C:\ORACLE\PRODUCT\10.2.0\ORADATA\TESTDB\USERS01.DBF'
CHARACTER SET EE8MSWIN1250
ALTER DATABASE OPEN RESETLOGS;
ALTER TABLESPACE TEMP ADD TEMPFILE 'C:\ORACLE\PRODUCT\10.2.0\ORADATA\TESTDB\TEMP01.DBF' REUSE;Is that correct?
About the RMAN backups: Wouldn't a 'CATALOG RECOVERY AREA' populate the controlfile with backup information again (I'm not using a recovery catalog in this case)?
Thanks for the help!
Regards,
Jure

Do I always need redo logs?

hi guys,
Is there a way to turn off redo logs being written to to make the database faster? I am not using ARCHIVELOGS as it is a test database, so I dont see of having any redo logs.
thanks

Hi,
No, You can't turn off the redo logs, Let’s conduct a brief summary about the redo process. When Oracle blocks are changed, including undo blocks, oracle records the changes in a form of vector changes which are referred to as redo entries or redo records. The changes are written by the server process to the redo log buffer in the SGA. The redo log buffer is then flushed into the online redo logs in near real time fashion by the log writer LGWR. (See Figure 1)
The redo logs are written by the LGWR when:
•     When a user issue a commit.
•     When the Log Buffer is 1/3 full.
•     When the amount of redo entries is 1MB.
•     Every three seconds
•     When a database checkpoint takes place. The redo entries are written before the checkpoint to ensure recover ability.
Redo log files record changes to the database as a result of transactions and internal Oracle server actions. (A transaction is a logical unit of work, consisting of one or more SQL statements run by a user.) Redo log files protect the database from the loss of integrity because of system failures caused by power outages, disk failures, and so on. Redo log files must be multiplexed to ensure that the information stored in them is not lost in the event of a disk failure. The redo log consists of groups of redo log files. A group consists of a redo log file and its multiplexed copies. Each identical copy is said to be a member of that group, and each group is identified by a number. The Log Writer (LGWR) process writes redo records from the redo log buffer to all members of a redo log group until the file is filled or a log switch operation is requested. Then, it switches and writes to the files in the next group. Redo log groups are used in a circular fashion.
Best practice tip:
Oracle recommends that redo log groups have at least two files per group, with the files distributed on separate disks or controllers so that no single equipment failure destroys an entire log group.
The loss of an entire log group is one of the most serious possible media failures because it can result in loss of data. The loss of a single member within a multiple-member log group is trivial and does not affect database operation, other than causing an alert to be published in the alert log.
Remember that redo logs heavily influence database performance because a commit cannot complete until the transaction information has been written to the logs. You must place your redo log files on your fastest disks served by your fastest controllers. If possible, do not place any other database files on the same disks as your redo log files. Because only one group is written to at a given time, there is no harm in having members from several groups on the same disk.+
Note: This is a extract of my paper: [Logging or Not Logging, This is the Question.|http://oraclenz.com/__oneclick_uploads/2008/08/redo_reduction_v_1_9.pdf]
I hope this will help you.
Regards,
Francisco Munoz Alvarez
www.oraclenz.com

Filled redo log files are available to LGWR for reuse

Hi,
Oracle version:
Oracle Database 10g Release 10.2.0.4.0 -
OS:Windows XP
In oracle documentation it is mentioned that:
Filled redo log files are available to LGWR for reuse depending on whether archiving is enabled.
*> If archiving is disabled (the database is in NOARCHIVELOG mode), a filled redo log file is available after the changes recorded in it have been written to the datafiles*.
Link for Documentation is:
http://docs.oracle.com/cd/B28359_01/server.111/b28310/onlineredo001.htm
My doubt is:
Redo Records are written to datafiles also??

user12141893 wrote:
Does it mean:
Suppose:
Online redo log files contains some redo entries and database buffer cache contains some data and this data belong to redo entries of redo log files.
Now this redo log file can't be reused until those (related) blocks of database buffer cache are written into datafiles.
This is sort of correct. If the log file would be filled up , LGWR would switch over to the next log group and would initiate a Log Switch which would further trigger DBWR to start checkpointing the content protected by this log group to the data file. By the time this operation would be going on, the Log group's members would have the status of Active and once it would be complete, the status would be marked to Inactive which means that this log group and its members can be reused by LGWR.
HTH
Aman....

Online redo logs vs standby redo logs

Hi All,
Oracle version : 10.2.0.4
OS : SunOS 5.10 Generic_118855-36 i86pc i386 i86pc
This might be a silly question for the experts :(
We are having 2 standby databases and 1 logical database. Everything is running fine , I have one confusion : My primary server having 3 online redo log files and 3 standby redo log files (on primary local), but as per the architecture standby redo logs should be on standby server.My question is whether standby redo logs on standby are online redo logs of standby server or standby redo logs of primary server. e.g If i perform a log switch on primary then what is the role of sync and affirm, will lgwr write parallel on online redo logs ,standby redo logs (of primary) or online redo logs (of primary) and online redo logs (which is known as standby redo logs on standby ). Please help me to understand the scenerio.
Thanks in advance!

RFS receives redo information from the primary database.
RFS can write the redo into standby redo logs or directly to archived redo logs. Each LNSn and ARCn process from the primary database has its own RFS process.
A standby redo log is used only when the database is in the standby role to store redo data received from the primary database. Standby redo logs form a separate pool of log file groups.
Configuring standby redo log files is highly recommended on all standby databases in a Data Guard configuration, including the primary database to aid in role reversal.
A standby redo log is required to implement:
• The maximum protection and maximum availability levels of data protection
• Real-time apply
• Cascaded redo log destinations
Standby redo logs are recommended for maximum performance data protection mode. Unless you are using the real-time apply feature, standby redo logs must be archived before the data can be applied to the standby database. The standby archival operation occurs automatically.

High redo log space wait time

Hello,
Our DB is having very high redo log space wait time :
redo log space requests 867527
redo log space wait time 67752674
LOG_BUFFER is 14 MB and having 6 redo logs groups and the size of redo log file is 500MB for each log file.
Also, the amount of redo generated per hour :
START_DATE START NUM_LOGS MBYTES DBNAME
2008-07-03 10:00 2 1000 TKL
2008-07-03 11:00 4 2000 TKL
2008-07-03 12:00 3 1500 TKL
Does increasing the size of LOG_BUFFER will help to reduce the redo log space wait ?
Thanks in advance ,
Regards,
Aman

Looking quickly over the AWR report provided the following information could be helpful:
1. You are currently targeting approx. 6GB of memory with this single instance and the report tells that physical memory is 8GB. According to the advisories it looks like you could decrease your memory allocation without tampering your performance.
In particular the large_pool_size setting seems to be quite high although you're using shared servers.
Since you're using 10.2.0.4 it might be worth to think about using the single SGA_TARGET parameter instead of the specifying all the single parameters. This allows Oracle to size the shared pool components within the given target dynamically.
2. You are currently using a couple of underscore parameters. In particular the "_optimizer_max_permutations" parameter is set to 200 which might reduce significantly the number of execution plans permutations Oracle is investigating while optimizing the statement and could lead to suboptimal plans. It could be worth to check why this has been set.
In addition you are using a non-default setting of "_shared_pool_reserved_pct" which might no longer be necessary if you are using the SGA_TARGET parameter as mentioned above.
3. You are using non-default settings for the "optimizer_index_caching" and "optimizer_index_cost_adj" parameters which favor index-access paths / nested loops. Since the "db file sequntial read" is the top wait event it might be worth to check if the database is doing too excessive index access. Also most of the rows have been fetched by rowid (table fetch by rowid) which could also be an indicator for excessive index access/nested loop usage.
4. You database has been working quite a lot during the 30min. snapshot interval: It processed 123.000.000 logical blocks, which means almost 0.5GB per second. Check the top SQLs, there are a few that are responsible for most of the blocks processed. E.g. there is a anonymous PL/SQL block that has been executed almost 17.000 times during the interval representing 75% of the blocks processed. The statements executed as part of these procedures might be worth to check if they could be tuned to require less logical I/Os. This could be related to the non-default optimizer parameters mentioned above.
5. You are still using the compatible = 9.2.0 setting which means this database could still be opened by a 9i instance. If this is no longer required, you might lift this to the default value of 10g. This will also convert the REDO format to 10g I think which could lead to less amount of redo generated. But be aware of the fact that this is a one-way operation, you can only go back to 9i then via a restore once the compatible has been set to 10.x.
6. Your undo retention is set quite high (> 6000 secs), although your longest query in the AWR period was 151 seconds. It might be worth to check if this setting is reasonable, as you might have quite a large undo tablespace at present. Oracle 10g ignores the setting if it isn't able to honor the setting given the current Undo tablespace size.
7. "parallel_max_servers" has been set to 0, so no parallel operations can take place. This might be intentional but it's something to keep in mind.
Regards,
Randolf
Oracle related stuff:
http://oracle-randolf.blogspot.com/
SQLTools++ for Oracle:
http://www.sqltools-plusplus.org:7676/
http://sourceforge.net/projects/sqlt-pp/

Groups and Member in Redo Log

Similar Messages

Maybe you are looking for