Redo log files are deleted, how to recover the database

Hi All,
I removed the redo01.log, redo02.log and redo03.log files of our Oracle database. And it caused the db to fail. Is there any way I can recover the database and startup database in normal mode? I do not need it to have all the latest data restored, I will be happy to just start the db and get going.
database is in arcive log mode.
Thanks

Hello,
You may try this if the database is mounted:
recover database until cancel;
cancel
alter database open resetlogs;Hope it can help.
Best regards,
Jean-Valentin

Similar Messages

Redo log files are not applied in DR of primary

Hi All,
I have a DR database of primary on QA Serevr. The Redo log files are not properly applied in the DR database.
The Oracle version is 11.2.0.1 Some of the files get shipped and applied to DR database automatically but not all.
SQL> select status, error from v$archive_dest where dest_id=2; gives following massage
ERROR ORA-16086: Redo data cannot be written to the standby redo log
Please suggest.
Regards,
Shashi

Hi,
Sorry for delay in response. Here I am attaching the error captured in standby database.
Please advise
alert_abc.log
RFS[1780]: Identified database type as 'physical standby': Client is LGWR SYNC pid 21855
Primary database is in MAXIMUM AVAILABILITY mode
Standby controlfile consistent with primary
Standby controlfile consistent with primary
RFS[1780]: No standby redo logfiles of file size 94371840 AND block size 512 exist
Clearing online log 16 of thread 0 sequence number 0
Errors in file /oracle/diag/rdbms/abc_location11/abc/trace/abc_rfs_27994.trc:
ORA-00367: checksum error in log file header
ORA-00315: log 16 of thread 0, wrong thread # 1 in header
ORA-00312: online log 16 thread 0: '/oracle/abc/origlogB/log_g116m1.dbf'
Mon Nov 14 00:49:16 2011
Clearing online log 9 of thread 0 sequence number 0
Errors in file /oracle/diag/rdbms/abc_location11/abc/trace/abc_arc0_15653.trc:
/oracle/diag/rdbms/abc_location11/abc/trace/abc_rfs_27994.trc
2011-11-14 00:49:19.385
DDE rules only execution for: ORA 312
START Event Driven Actions Dump -
END Event Driven Actions Dump -
START DDE Actions Dump -
Executing SYNC actions
START DDE Action: 'DB_STRUCTURE_INTEGRITY_CHECK' (Async) -
DDE Action 'DB_STRUCTURE_INTEGRITY_CHECK' was flood controlled
END DDE Action: 'DB_STRUCTURE_INTEGRITY_CHECK' (FLOOD CONTROLLED, 1 csec) -
Executing ASYNC actions
END DDE Actions Dump (total 0 csec) -
ORA-00367: checksum error in log file header
ORA-00315: log 16 of thread 0, wrong thread # 1 in header
ORA-00312: online log 16 thread 0: '/oracle/abc/origlogB/log_g116m1.dbf'
DDE rules only execution for: ORA 312
START Event Driven Actions Dump -
END Event Driven Actions Dump -
START DDE Actions Dump -
Executing SYNC actions
START DDE Action: 'DB_STRUCTURE_INTEGRITY_CHECK' (Async) -
DDE Action 'DB_STRUCTURE_INTEGRITY_CHECK' was flood controlled
END DDE Action: 'DB_STRUCTURE_INTEGRITY_CHECK' (FLOOD CONTROLLED, -641 csec) -
Executing ASYNC actions
END DDE Actions Dump (total 0 csec) -
ORA-19527: physical standby redo log must be renamed
ORA-00312: online log 16 thread 0: '/oracle/abc/origlogB/log_g116m1.dbf'
Error 19527 clearing SRL 16
/oracle/diag/rdbms/abc_location11/abc/trace/abc_arc0_15653.trc
ORA-19527: physical standby redo log must be renamed
ORA-00312: online log 9 thread 0: '/oracle/abc/origlogA/log_g19m1.dbf'
Error 19527 clearing SRL 9
DDE rules only execution for: ORA 312
START Event Driven Actions Dump -
END Event Driven Actions Dump -
START DDE Actions Dump -
Executing SYNC actions

How to recover the database when some of the archive log file get deleted.

I am facing a problem with Oracle database, which is related to archivelogs.
Our development database is running in archivelog mode, but we don't have backups scheduled and have no recovery catalog.
When the database was in running condition, disk got full, so some archivelogs were deleted manually.
After this they restarted the DB, and now DB is not coming up. Errors are as follows:
SQL> startup
ORACLE instance started.
Total System Global Area 1444383504 bytes
Fixed Size 731920 bytes
Variable Size 486539264 bytes
Database Buffers 956301312 bytes
Redo Buffers 811008 bytes
Database mounted.
ORA-01589: must use RESETLOGS or NORESETLOGS option for database open
SQL> alter database open resetlogs;
alter database open resetlogs
ERROR at line 1:
ORA-01113: file 1 needs media recovery
ORA-01110: data file 1: '/export/home/oracle/dev/ADVFRW/ADVFRW.system'
SQL> recover datafile '/export/home/oracle/dev/ADVFRW/ADVFRW.system'
ORA-00283: recovery session canceled due to errors
ORA-01610: recovery using the BACKUP CONTROLFILE option must be done
SQL> recover database using backup controlfile;
ORA-00279: change 215548705 generated at 09/02/2008 17:06:10 needed for thread
1
ORA-00289: suggestion :
/export/home/oracle/dev/ADVFRW/ADVFRW.archivelog1/LOG_ADVFRW_1107_1.ARC
ORA-00280: change 215548705 for thread 1 is in sequence #1107
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
/export/home/oracle/dev/ADVFRW/ADVFRW.archivelog1/LOG_ADVFRW_1107_1.ARC
ORA-00308: cannot open archived log
'/export/home/oracle/dev/ADVFRW/ADVFRW.archivelog1/LOG_ADVFRW_1107_1.ARC'
ORA-27037: unable to obtain file status
SVR4 Error: 2: No such file or directory
Additional information: 3
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
CANCEL
Media recovery cancelled.
SQL>
1. How to recover the database and bring it online
Any help will be highly appreciated.
With Regards
Hemant Joshi
Edited by: hem_Kec on Sep 7, 2008 9:07 AM

Hi,
Archive log files are the copies of redolog files.As redo log files are circularly overwritten,oracle generates archive log file of the corresponding redo logfiles being overwritten.So if you have a backup that dates back to 10 am in the morning and if your database creashed at 3 pm,you cannot use the redo log files alone as they have incomplete information.To completely recover the database upto 3 pm,you need archive log files generated between 10 am to 3 pm. In your case since you are missing one archive log file,you cannot perform complete recovery and hence would suffer data loss.

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....

Redo log files are not applying to standby database

Hi everyone!!
I have created standby database on same server ( windows XP) and using oracle 11g . I want to synchronize my standby database with primary database . So I tried to apply redo logs from primary to standby database as follow .
My standby database is open and Primary database is not started (instance not started) because only one database can run in Exclusive Mode as DB_NAME is same for both database. I run the following command on the standby database.
SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;
It returns "Database altered" . But when I checked the last archive log on primary database, its sequence is 189 while on standby database it is 177. That mean archived redo logs are not applied on standby database.
The tnsnames.ora file contains entry for both service primary & standby database and same service has been used to transmit and receive redo logs.
1. How to resolve this issue ?
2.Is it compulsory to have Primary database open ?
3. I have created standby control file by using command
SQL> ALTER DATABASE CREATE STANDBY CONTROLFILE AS ‘D:\APP\ORACLE\ORADATA\TESTCAT\CONTROLFILE\CONTROL_STAND1.CTL‘;
So database name in the standby control file is same as primary database name (PRIM). And hence init.ora file of standby database also contains DB_NAME = 'PRIM' parameter. I can't change it because it returns error of mismatch database name on startup. Should I have different database name for both or existing one is correct ?
Can anybody help me to come out from this stuck ?
Thanks & Regards
Tushar Lapani

Thank you Girish. It solved my redo apply problem. I set log_archive_dest parameter again and then I checked archive redo log sequence number. It was same for both primary and standby database. But still table on standby database is not being refresh.
I did following scenario.
1. Inserted 200000 rows in emp table of Scott user on Primary database and commit changes.
2. Then I synchronized standby database by using Alter database command. And I also verify that archive log sequence number is same for both database. It mean archived logs from primary database has been applied to standby database.
3. But when I count number of rows in emp table of scott user on standby database, it returns only 14 rows even of redo log has been applied.
So my question is why changes made to primary database is not reflected on standby database although redo logs has been applied ?
Thanks

DB6 - Log files accidentally deleted - How to recreate them?

Hello community,
we found that all DB2 log files of a Solution Manager were manually deleted. The instance was down for some time, so we did not realize the problem immediately, but only now on the restart
We are able to start DB2, but SAP can't connect and this error is reported in the log from the R3trans -d
An I/O error occurred while accessing the database STATE=58030
In the db2diag there are a lot of errors related to missing log file:
RETCODE : ZRC=0x860F000A=-2045837302=SQLO_FNEX "File not found."
DIA8411C A file "S0000016.LOG" could not be found.
There is a procedure to recreate the DB2 log files?
Best Regards,
Valerio

Hi Valerio,
Without the log files the db does not know what transactions are open and hwat state it is in.
The logs cannot be just recreated.
Do you have any possibility to recover the logs? Could they have been moved to another location or were they completey deleted? Do you have a log mirror path set?
If deleted then you could either restore from your last good backup and restore to the last point where you have logs or you will need to open a message to ask assistance in solving this.
Regards,
Paul

Log file corrupt and can't open the database.

I use Replication Manager to manage my Replication; and there is only one site currently in my application.
I killed the App process with signal -9. (ie. $ kill -9 appID).
Then I try to restart the App, but the event_callback function got a PANIC event when to open the envirment.
The open flag is:
flags = DB_CREATE | DB_INIT_LOCK | DB_INIT_LOG | DB_INIT_MPOOL |
DB_INIT_REP | DB_INIT_TXN | DB_RECOVER | DB_THREAD;
ret = dbenv->open(dbenv, path, flags | DB_SYSTEM_MEM, 0);
What's the reason cause this problem?
How can recover it ?
The logs list as below:
[D 11/19 09:44] dbpf using shm key: 977431433
[E 11/19 09:44] [src/io/dbpf-mgmt.c, 400]
[E 11/19 09:44] yuga: DB_LOGC->get: LSN 1/9776: invalid log record header
[E 11/19 09:44] yuga: Log file corrupt at LSN: [1][9906]
[E 11/19 09:44] yuga: PANIC: Invalid argument
[E 11/19 09:44] [src/io/dbpf-mgmt.c] Rep EventGot a panic: Invalid argument (22)
Edited by: dbnicker on Nov 18, 2010 6:08 PM

First, what version of Berkeley DB are you running and on what system?
The error indicates something amiss in the log. The LSN values are quite
small. Can you run 'db_printlog -N -h <env path>' and post the log
contents?
If you are using BDB 5.0 or later, can you also post the contents of
the __db.rep.diag00 file in the environment home directory? Thanks.
Sue LoVerso
Oracle

NXT files (once deleted how to recover?)

Hi,
I am using the brick from LEGO Mindstorms NXT 2.0
I accidentally deleted the file RedData.dat from my NXT, and I need that for one of my programs.
Even when I tell the program to "write to red data file", it does not recreate the file, so I'm left with no data to show.
I am using all three data files, so I cannot simply just switch to another one.
I have also tried telling the NXT to create a new file when it runs the program, called RedData.dat.
What happens when I do this is that I get erratic results. Instead of a nice curve, I get lines that jump all over the place.
I am programming the NXT with NI LabVIEW 2009. The place where I deleted RedData.dat is from the NXT Terminal.
I view the data using the Data Viewer.
Also, I am trying to log motor rotations.
Thanks for your help.
Solved!
Go to Solution.

dluu wrote:
Hi,
I am using the brick from LEGO Mindstorms NXT 2.0
I accidentally deleted the file RedData.dat from my NXT, and I need that for one of my programs.
Even when I tell the program to "write to red data file", it does not recreate the file, so I'm left with no data to show.
I am using all three data files, so I cannot simply just switch to another one.
I have also tried telling the NXT to create a new file when it runs the program, called RedData.dat.
What happens when I do this is that I get erratic results. Instead of a nice curve, I get lines that jump all over the place.
I am programming the NXT with NI LabVIEW 2009. The place where I deleted RedData.dat is from the NXT Terminal.
I view the data using the Data Viewer.
Also, I am trying to log motor rotations.
Thanks for your help.
Do you have the NXT tethered? What happens if you run the code the opposite way? (i.e. if it's tethered, download the code directly and run, if it isn't, try tethering it)
Also, have you made sure to update the firmware on the NXT? What is its version?

Private strand flush not complete how to find optimal size of redo log file

hi,
i am using oracle 10.2.0 on unix system and getting Private strand flush not complete in the alert log file. i know this is due to check point is not completed.
I need to increase the size of redo log files or add new group to the database. i have log file switch (checkpoint incomplete) in the top 5 wait event.
i can't change any parameter of database. i have three redo log group and log files are of 250MB size. i want to know the suitable size to avoid problem.
select * from v$instance_recovery;
RECOVERY_ESTIMATED_IOS ACTUAL_REDO_BLKS TARGET_REDO_BLKS LOG_FILE_SIZE_REDO_BLKS LOG_CHKPT_TIMEOUT_REDO_BLKS LOG_CHKPT_INTERVAL_REDO_BLKS FAST_START_IO_TARGET_REDO_BLKS TARGET_MTTR ESTIMATED_MTTR CKPT_BLOCK_WRITES OPTIMAL_LOGFILE_SIZE ESTD_CLUSTER_AVAILABLE_TIME WRITES_MTTR WRITES_LOGFILE_SIZE WRITES_LOG_CHECKPOINT_SETTINGS WRITES_OTHER_SETTINGS WRITES_AUTOTUNE WRITES_FULL_THREAD_CKPT
625 9286 9999 921600 9999 0 9 112166207 0 0 219270206 0 3331591 5707793please suggest me or tell me the way how to find out suitable size to avoid problem.
thanks
umesh

How often should a database archive its logs
Re: Redo log size increase and performance
Please read the above thread and great replies by HJR sir. I think if you wish to get concept knowledge, you should add in your notes.
"If the FAST_START_MTTR_TARGET parameter is set to limit the instance recovery time, Oracle automatically tries to checkpoint as frequently as necessary. Under this condition, the size of the log files should be large enough to avoid additional checkpointing due to under sized log files. The optimal size can be obtained by querying the OPTIMAL_LOGFILE_SIZE column from the V$INSTANCE_RECOVERY view. You can also obtain sizing advice on the Redo Log Groups page of Oracle Enterprise Manager Database Control."
Source:http://download-west.oracle.com/docs/cd/B13789_01/server.101/b10752/build_db.htm#19559
Pl also see ML Doc 274264.1 (REDO LOGS SIZING ADVISORY) on tips to calculate the optimal size for redo logs in 10g databases
Source:Re: Redo Log Size in R12
HTH
Girish Sharma

Need to understand when redo log files content is wrote to datafiles

Hi all
I have a question about the time when redo log files are wrote to the datafiles
supposing that the database is in NOARCHIVELOG mode, and all redo log files are filled, the official oracle database documentation says that: *a filled redo log file is available
after the changes recorded in it have been written to the datafiles* witch mean that we just need to have all the redo log files filled to "*commit*" changes to the database
Thanks for help
Edited by: rachid on Sep 26, 2012 5:05 PM

rachid wrote:
the official oracle database documentation says that: a filled redo log file is available after the changes recorded in it have been written to the datafiles It helps if you include a URL to the page where you found this quote (if you were using the online html manuals).
The wording is poor and should be modified to something like:
<blockquote>
+"a filled online redo log file is available for re-use after all the data blocks that have been changed by change vectors recorded in the log file have been written to the data files"+
</blockquote>
Remember if a data block that is NOT an undo block has been changed by a transaction, then an UNDO block has been changed at the same time, and both change vectors will be in the redo log file. The redo log file cannot, therefore, be re-used until the data block and the associated UNDO block have been written to disc. The change to the data block can thus be rolled back (uncommitted changes can be written to data files) because the UNDO is also available on disc if needed.
If you find the manuals too fragmented to follow you may find that my book, Oracle Core, offers a narrative description that is easier to comprehend.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
Author: <b><em>Oracle Core</em></b>

Problem in creating database -Missing Redo log file

I am try to create a new database using DBCA .While creating a database it shows the error oracle instance terminated.Force Disconnected.
My alert log file is
Errors in file /u01/app/oracle/diag/rdbms/oracl/oracl/trace/oracl_ora_5424.trc:
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: '/u01/app/oracle/oradata/oracl/redo01.log'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3
Wed Nov 06 10:07:27 2013
Errors in file /u01/app/oracle/diag/rdbms/oracl/oracl/trace/oracl_ora_5424.trc:
ORA-00313: open failed for members of log group 2 of thread 1
ORA-00312: online log 2 thread 1: '/u01/app/oracle/oradata/oracl/redo02.log'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3
Errors in file /u01/app/oracle/diag/rdbms/oracl/oracl/trace/oracl_ora_5424.trc:
ORA-00313: open failed for members of log group 3 of thread 1
ORA-00312: online log 3 thread 1: '/u01/app/oracle/oradata/oracl/redo03.log'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3
Wed Nov 06 10:07:38 2013
Setting recovery target incarnation to 2
Wed Nov 06 10:07:38 2013
Assigning activation ID 1876274518 (0x6fd5ad56)
Thread 1 opened at log sequence 1
Current log# 1 seq# 1 mem# 0: /u01/app/oracle/oradata/oracl/redo01.log
Successful open of redo thread 1
Wed Nov 06 10:07:38 2013
MTTR advisory is disabled because FAST_START_MTTR_TARGET is not set
Wed Nov 06 10:07:38 2013
SMON: enabling cache recovery
Errors in file /u01/app/oracle/diag/rdbms/oracl/oracl/trace/oracl_ora_5424.trc (incident=1345):
ORA-00600: internal error code, arguments: [kpotcgah-7], [12534], [ORA-12534: TNS:operation not supported
Incident details in: /u01/app/oracle/diag/rdbms/oracl/oracl/incident/incdir_1345/oracl_ora_5424_i1345.trc
Wed Nov 06 10:07:46 2013
Trace dumping is performing id=[cdmp_20131106100746]
Errors in file /u01/app/oracle/diag/rdbms/oracl/oracl/trace/oracl_ora_5424.trc:
ORA-00600: internal error code, arguments: [kpotcgah-7], [12534], [ORA-12534: TNS:operation not supported
Error 600 happened during db open, shutting down database
USER (ospid: 5424): terminating the instance due to error 600
Instance terminated by USER, pid = 5424
ORA-1092 signalled during: alter database "oracl" open resetlogs...
ORA-1092 : opiodr aborting process unknown ospid (5424_47935551851664)
Wed Nov 06 10:07:47 2013
ORA-1092 : opitsk aborting process
251,1 95%

>I am try to create a new database using DBCA
>Please help me to resolve this issue.My redo log file was missing
DROP and recreate the database. It is a *new* database without any data.
Check what datafile locations and redo log file locations you specify when creating the new database. Check if you have permissions and enough disk space.
Hemant K Chitale

Deleted redo log files

hi everbody,
i use oracle 9.2 and 3 redo log files was created when installation. Now, i could not open database because two of redo log files was deleted (that i haven't understood how deleted.) So what can i do ? recovery is possible ? if poosibel how ?
NOTES :
my database does not work Archive mode and give below error messages...
Total System Global Area 126950220 bytes
Fixed Size 453452 bytes
Variable Size 96468992 bytes
Database Buffers 29360128 bytes
Redo Buffers 667648 bytes
Database mounted.
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: 'C:\ORACLE\ORADATA\ABUZER\REDO01.LOG'

thanks everbody. i couldn't give information because some problems was internet connections. i solved problems. i found command and info in the Oracle 8i Admin Guide documentation. first i dropped two log groups whose files are missing then recreate these these log groups with redo log files..before that i start up an new instance, but do not mount the database. after that i use commands like below :
ALTER DATABASE DROP LOGFILE GROUP 1 ;
ALTER DATABSE DROP LOGFILE GROUP 2 ;
ALTER DATABASE ADD LOGFILE GROUP 1 ('C:\...\REDO01.LOG') SIZE 1020400K
ALTER DATABASE ADD LOGFILE GROUP 2 ('C:\...\REDO02.LOG') SIZE 1020400K
thanks everbody...

Recover from missing files(redo log file/control file) and state of the DB

Hello,
i hv go through the doc. as well. But have some doubts what will happen in each on these situations.
Pls help me to clarify these!
Scenario is like this;
hv 3 redo log files - multiplxed
hv 3 control files - multiplxed
- What will happen if 1 redo log file missing when starting the DB?
- What will happen if 1 redo log file missing when using(performing operations) the DB?
(will it recover automatically/db abort/even redo log lost will the DB run as usual... ?)
-How to recover this lost redo log?
- What will happen if 1 control file missing when starting the DB?
- What will happen if 1 control file missing when using(performing operations) the DB?
(will it recover automatically/db abort/even control file lost will the DB run as usual... ?)
-How to recover this lost redo log?
thanks

- What will happen if 1 redo log file missing when starting the DB?IF you have multiplexed the members you can drop the lost file and will be able to open the DB
What will happen if 1 redo log file missing when using(performing operations) the DB?Again if multiplexed it will drop a warinign in the alert log and contnue to write on othere members
http://download.oracle.com/docs/cd/B19306_01/backup.102/b14191/recoscen.htm#sthref1385
- What will happen if 1 control file missing when starting the DB?Just remove the entry from the init.ora and start the DB
What will happen if 1 control file missing when using(performing operations) the DB?Will shutdown

Question about how Oracle manages Redo Log Files

Good morning,
Assuming a configuration that consists of 2 redo log groups (Group A and B), each group consisting of 2 disks (Disks A1 & A2 for Group A and Disks B1 and B2 for group B). Further, let's assume that each redo log file resides by itself in a disk storage device and that the device is dedicated to it. Therefore in the above scenario, there are 4 disks, one for each redo log file and, each disk contains nothing else other than a redo log file. Furthermore, let's assume that the database is in ARCHIVELOG mode and that the archive files are stored on yet another different set of devices.
sort of graphically:
    GROUP A             GROUP B
      A1                  B1
      A2                  B2The question is: When the disks that comprise Group A are filled and Oracle switches to the disks in Group B, can the disks in Group A be taken offline, maybe even physically removed from the system if necessary, without affecting the proper operation of the database ? Can the Archiver process be temporarily delayed until the disks (that were removed) are brought back online or is the DBA forced to wait until the Archiver process has finished creating a copy of the redo log file into the archive ?
Thank you for your help,
John.

Hello,
Dropping Log Groups
To drop an online redo log group, you must have the ALTER DATABASE system privilege. Before dropping an online redo log group, consider the following restrictions and precautions:
* An instance requires at least two groups of online redo log files, regardless of the number of members in the groups. (A group is one or more members.)
* You can drop an online redo log group only if it is inactive. If you need to drop the current group, first force a log switch to occur.
* Make sure an online redo log group is archived (if archiving is enabled) before dropping it. To see whether this has happened, use the V$LOG view.
SELECT GROUP#, ARCHIVED, STATUS FROM V$LOG;
GROUP# ARC STATUS
1 YES ACTIVE
2 NO CURRENT
3 YES INACTIVE
4 YES INACTIVE
Drop an online redo log group with the SQL statement ALTER DATABASE with the DROP LOGFILE clause.
The following statement drops redo log group number 3:
ALTER DATABASE DROP LOGFILE GROUP 3;
When an online redo log group is dropped from the database, and you are not using the Oracle Managed Files feature, the operating system files are not deleted from disk. Rather, the control files of the associated database are updated to drop the members of the group from the database structure. After dropping an online redo log group, make sure that the drop completed successfully, and then use the appropriate operating system command to delete the dropped online redo log files.
When using Oracle-managed files, the cleanup of operating systems files is done automatically for you.
Your Database wont be affected as you can operate with 2 redo log files in each group as The minimum number of redo log files required in a database is two because the LGWR (log writer) process writes to the redo log files in a circular manner. so the process will hang becuase you are having 2 only groups if you want to remove 1 add a third one and make it the current group then remove the one you want to be offline.
Please refer to:
http://download.oracle.com/docs/cd/B10500_01/server.920/a96521/onlineredo.htm#7438
Kind regards
Mohamed
Oracle DBA

How to reduce the size of redo log files

Hi,
I am using Oracle Database 9.2.0.1.0. My present redo log files are of 100 MB each
(redo01.log,redo02.log,redo03.log) which tooks more time to swicth the logs.
I want to change the size to 20MB each so that log switcjing will be faster.
Please let me know the exact step to resize the redo log files so that Ican change it.
Regards,
Indraneel

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