Removing Redo Log Files? What's Normal?

Hello,
I'm new to Oracle and I've been using Informix for years. We currently have Oracle 9.2 running on Windows 2000 Server machine and apparently the redo log files keep filling up the disk drives they reside on. This is happening about every two weeks since we go out and delete the files when we remember.
My question is does Oracle have a "normal" way of removing old redo logs automatically rather than having to remove them manually? In the Informix world I can set the logical logs so that they write over previously used logs once they are no longer used. Is there a similar way to configure Oracle?
Thanks for helping out.
Gregg Walker

Do not delete your old log files: you need them.
That's how Oracle does recovery when you lose a datafile or a drive. You copy over the missing stuff from your back-up and then Oracle re-applies the chnages from the REDO logs thereby bringing your database back up to date. No work lost. Result!
Of course, if you don't take up a backup then holding on to REDO logs is pointless. In which case, set the database to run in NOARCHIVELOG mode.
However, I strongly advise you to run in ARCHIVELOG mode. You may find this part of the administrator's guide informative: http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96521/archredo.htm#4553
Cheers, APC

Similar Messages

What is online redo log files???

Dear All,
I m bit confused with redo log files.what is need of back up of redo log files?????As i m new in the Basis please tell me i always get confused with redo log files and archive files.
Thanx and reagard's
Ashok

In Oracle you have a number of online redo log files.
In an typical SAP installation you have two directories:
origlogA and origlogB
origlogA contains online redo log 1 and 3 and
origlogB contains online redo log 2 and 4.
In most installation you also have mirrlogA and mirrlogB, which the name tells, is mirrors of origlogA and origlogB.
Now, the online redo logs are circular,
so when 1 gets full oracle jumps to number 2.
At the same time oracle's archiver process starts to copy
online redo log number 1 to a file on disk.
This files are also known as archive redo logs.
In an recovery situation you might do with just the online redo logs,
but usually a combination of both online and archive redo logs is needed.
During database backup, you also backup the online redo logs
You also need to backup (backup twice then delete) archive redo logs.
the archive redo logs are your way back from the restored database to the last transaction of the database.
If one archive redo log is missing, you have to stop you recovery there and loose the rest of the transactions done in the database.

Redo log file thread

Dear All,
In am using oracle 10.2.0.4.0 in RHEL 4.
In my current set we had two node RAC (tims1,tims2) db_name (tims).
One of the node has failed(hard disk),Failed node information has been remove from OCR(all the cluster component like...ons,vip,listener,instance).
My Question IS:After Removing All the Cluster Component does it remove redo log files associate with the failed instance.
Redo logfile Before Node Delete:
SQL> select member from v$logfile;
MEMBER
/database/tims/redo02.log
/database/tims/redo01.log
/database/tims/redo03.log
/database/tims/redo04.log
Redo Logfile After Node Delete
SQL> select member from v$logfile;
MEMBER
/database/tims/redo02.log
/database/tims/redo01.log
/database/tims/redo03.log
/database/tims/redo04.log
It means redo logfile has not been removed.
Please help me what are the redo thread i will have to remove.
SQL> select group#,sequence#,thread# from v$log;
    GROUP# SEQUENCE#    THREAD#
         1      28868          1
         2      28867          1
         3      29327          2
         4      29328          2
Thanks &Regards
Monoj Das

monoj wrote:
Dear All
SQL> select group#,sequence#,thread# from v$log;
    GROUP# SEQUENCE#    THREAD#
         1      28868          1
         2      28867          1
         3      29327          2
         4      29328          2
According to my above query, thread# for group 1,2 is showing as 1 but the thread has been remove from cluster is there any use of those redo log.
Thanks and Regards
Monoj Das
Please leave your theories aside and read the replies given in the thread. The logs are going to stay as they are (should be) on the shared storage. Why you are hard-bent to remove these log files anyways? Are you not willing to add the other instance? RAC db with just one instance is really not of much use.
Aman....

Standby redo log file

Hi,
From oracle document i know in the standby side the RFS process writes to Standby redo log file -> archive log and the MRP procees applys the archive logs to the standby database.
my question is ,if we dont create standby redo log file what happens?

Hello;
When redo is received by an RFS on the standby , the RFS process writes the redo data into archived redo logs or optionally to the SRL.
Standby Redo Logs is where the RFS process at your Standby database writes incoming redo, they help performance because the RFS does not have to create the Archive log file.
Standby redo logs are a component of the Data Guard setup. They should be the same size as the redo logs on the Primary.
Standby Redo Logs do not not to be multiplexed.
I would create SRL them on both the Primary and the Standby. Think of it as one database in either Standby or Primary Mode. If you have to switchover you still need them.
If you have SRL's setup and need to do either a failover or switchover it should occur faster and safer.
Best Regards
mseberg

How to remove a redo log file

Hi Experts,
I want to remove a wrong redo log file from 10G R2 database in window.
how to do that without loss data?
my steps as
1. alter system switch logfile;
2. select * from v$log;
which ARC and sataus do I can drop redo log file based on above SQL
no archive and active status?
ALso Which account should I do above action?
fExamp, system account added redo log file, i only
can drop by system? how about sys?
Thanks help in detail steps
Jim
Edited by: user589812 on Dec 23, 2008 4:35 PM

Jim,
Check this link out for how to drop a redo log file
Make sure a redo log group is archived (if archiving is enabled) before dropping it. To see whether this has happened, use the V$LOG view.
http://download.oracle.com/docs/cd/B19306_01/server.102/b14231/onlineredo.htm#i1006489
SELECT GROUP#, ARCHIVED, STATUS FROM V$LOG;
   GROUP# ARC STATUS
        1 YES ACTIVE
        2 NO CURRENT
        3 YES INACTIVE
        4 YES INACTIVE
Drop a 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;

Online redo log files being removed physically

Grid Infra version: 11.2.0.4
RDBMS Version: 11.2.0.4
Although this is a RAC DB, this is not a RAC-specific question. Hence posting it here.
Few months back, I remember issuing a command similair to below (DROP LOGFILE GROUP ...) and the redo log files were still physically present in the diskgroup.
If I remember correctly, the file is not deleted physical so that we can use the REUSE functionality (ALTER DATABASE ADD LOGFILE MEMBER '+REDO/orcl/onlinelog/redo1b.log' reuse to group 11; ) ie. you can use the REUSE command to add the logfile of the same name which is physically present in OS Filesystem/Diksgroup to redo log group.
But today, after I issued the below command, I checked the diskgroup location from ASMCMD
SQL> alter database drop logfile group 31;
Database altered.
From ASMCMD, I can that the file has disappeared physically. Is this a new feature with 11.2.0.4 or am I missing something here ?
ASMCMD> ls +DATA/msblprd/onlinelog/group_31.548.833154995
ASMCMD-8002: entry 'group_31.548.833154995' does not exist in directory '+DATA/msblprd/onlinelog/'

Just to add to what Aman has said.
It is a bad practice not to let OMF decide the placement of Online redo logs because of this issue especially when you use ASM.
Executing rm command in Linux/Unix is easy but Dropping ASM aliases in the disk group can be a hassle.
This is documented.
"When a redo log member is dropped from the database, the operating system file is not deleted from disk. Rather, the control files of the associated database are updated to drop the member from the database structure. After dropping a redo log file, ensure that the drop completed successfully, and then use the appropriate operating system command to delete the dropped redo log file."
http://docs.oracle.com/cd/E11882_01/server.112/e25494/onlineredo.htm#ADMIN11324
BTW . You don't even need to set db_create_online_log_dest_n to enable OMF for ORLs.
SQL> show parameter log_dest
NAME                                 TYPE        VALUE
db_create_online_log_dest_1          string
db_create_online_log_dest_2          string
db_create_online_log_dest_3          string
db_create_online_log_dest_4          string
db_create_online_log_dest_5          string
SQL> show parameter db_create_file_dest
NAME                                 TYPE        VALUE
db_create_file_dest                  string      +MBL_DATA
alter database add logfile thread 4
group 31 ('+MBL_DATA','+MBL_FRA') size 4096M,
group 32 ('+MBL_DATA','+MBL_FRA') size 4096M,
group 33 ('+MBL_DATA','+MBL_FRA') size 4096M,
group 34 ('+MBL_DATA','+MBL_FRA') size 4096M ;
Database altered.
And redo logs will be neatly placed as shown below
   INST     GROUP# MEMBER                                             STATUS           ARC
         4         31 +MBL_DATA/bsblprd/onlinelog/group_31.276.832605441 UNUSED           YES
                      +MBL_FRA/bsblprd/onlinelog/group_31.297.832605445 UNUSED           YES
                   32 +MBL_DATA/bsblprd/onlinelog/group_32.547.832605451 UNUSED           YES
                      +MBL_FRA/bsblprd/onlinelog/group_32.372.832605457 UNUSED           YES
                   33 +MBL_DATA/bsblprd/onlinelog/group_33.548.832605463 UNUSED           YES
                      +MBL_FRA/bsblprd/onlinelog/group_33.284.832605469 UNUSED           YES
                   34 +MBL_DATA/bsblprd/onlinelog/group_34.549.832605475 UNUSED           YES
                      +MBL_FRA/bsblprd/onlinelog/group_34.359.832605481 UNUSED           YES

What is the purpose of standby redo log files

Hi,
What is the purpose of the standby redo log files in DR?
what if the standby redo log files are created? or else not created?
Please explain
Thanks

3.1.3 Configure a Standby Redo LogA standby redo log is required for the maximum protection and maximum availability modes and the LGWR ASYNC transport mode is recommended for all databases. Data Guard can recover and apply more redo data from a standby redo log than from archived redo log files alone.
You should plan the standby redo log configuration and create all required log groups and group members when you create the standby database. For increased availability, consider multiplexing the standby redo log files, similar to the way that online redo log files are multiplexed.>
Reference http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/create_ps.htm#i1225703
HTH
Anand

Commit Completes although current online redo log file have been removed.

Although i have removed current online redo log file in linux os (Oracle Linux),when i type "commit" it says that "commit complete".
Is this fair for this princip?*:" if Only when all redo records associated with a given transaction are safely on disk in the online logs is the user process notified that the transaction has been committed."*
I think that it can lead to loss of data in some cases..I'm using Oracle 11g R2 on OEL (x64)..
Can anyone explain me ? I'm getting stuck in this situation..
P.S : I haven't multiplexed current ORL group files...

Javid wrote:
Although i have removed current online redo log file in linux os (Oracle Linux),when i type "commit" it says that "commit complete".
Is this fair for this princip?*:" if Only when all redo records associated with a given transaction are safely on disk in the online logs is the user process notified that the transaction has been committed."*
I think that it can lead to loss of data in some cases..I'm using Oracle 11g R2 on OEL (x64)..
Can anyone explain me ? I'm getting stuck in this situation..
In *nix, a file that is open by a process isn't really deleted until the process that has it completes. So even though you 'deleted' a redo log, oracle is still holding it. As soon as you stop your database (maybe even as soon as the db does a log switch) the redo will really be gone and no longer available. consider the implications for archive logging.
P.S : I haven't multiplexed current ORL group files...You need to fix that. the online logs are the achilles heel of the database. That's why it is standard practice to multiplex them.

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.

What will happen when redo log file or archive log file, which is yet to be

What will happen when redo log file or archive log file, which is yet to be read by logminer is corrupted? It seems that the captures process hangs between “Paused for flow control” and “Enqueuing Messages”. How to come out of this condition without recreating the captures process?
Any clue is helpful
Thanks in advance for your help.

Basically you can't skip SCN since it will result in a data integrity issues (say you had skipped some inserts and later there will be some updates to a not replicated data).
Streams maintain their own checkpoint tables with transaction related stuff. So there is no way you can jump over a range of SCN's without recreating capture.
The only thing you can try - temporary give capture process a rule without any objects. But it will need to mine through the redo anyway.

What is a redo log file? can anyone explain in simple terms

I am confused between redo log file and physical datafile can anyone explain in simple terms
Thank u
Regards,
Vijay

See Overview of Physical Database Structures

Redo log files in case of NOARCHIVELOG Mode.

Question is related with the oracle architure..
database requires a minimum of two redo log files to guarantee that one is always available for writing while the other is being archived, this sounds perfect when DB is running in ARCHIVELOG mode but at the same time it also forces database to have 2 redo log files even when the DB is running in NOARCHIVELOG mode?
Any particular reason..
I would look for reasons not answers on what redo log is and what information it holds etc..

pgoel wrote:
If you had only one file all further changes would have to stop until all changed data blocks had been written to disc. By insisting on a minimum of two log files Oracle can allow the log writer to fill the second log file as the database writer writes out the dirty blocks covered by changes desrcibed in the first log file.What about having a big size redo log file instead of two? Checkppoint being initiated when the redo log file is half filled
I mean, understand the logic, two is better, even best.. but still not getting convinced. I am just trying to think, can not Oracle work with 1 group with 1 big file..specailly when Noarch mode ? Having
Edited by: pgoel on Mar 12, 2011 7:27 PMNo, you still didn't understand and I am not sure how else we can say it. Okay, think about log groups as two buckets which are used to fill the redo content. The LGWR is filling one bucket at a time till it can't accept any more content. Once filled, rather than spilling the content out, it jumps over to the second bucket. Now, taking your statement of big sized redo, Pgoel, it doesn't matter how big sized bucket you bring in, eventually it will fill in. Its not possible that you wont be able to fill it , it just would take more longer than the normal timings. Thats all. So in any case , you need the second bucket. And I am not sure that why you are struck on the archivelog mode. I hope you do understand that its an optional mode. This means, this may or may not be there. If there, its a good thing that before doing the flush of the redo content, Oracle would be able to save the contents in the archived (think about the name, it's very meaning is to preserve, to archive) log file. If not, the redo content wuold be lost and there won't be any record of transactions leaving you to reenter the lost transactions. Its a meaningless point on which you are struck i.e. the archive or no-archivelog mode. Be it whatever, Oracle would still need minimum of the two log groups.
HTH
Aman....

How to clean redo log file?

Hi, guys:
I need to migrate data from external tables to normal tables. But the connection is always frozen half the way of executing script. The error message is ORA-00257. it looks redo log file is full. I tried to delete redo log file with RMAN, but I got this error message:
delete archivelog until time 'trunc(sysdate)';
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=43 device type=DISK
specification does not match any archived log in the repository
Any suggestion would be appreciated.
Sam

lxiscas wrote:
Hi, guys:
I need to migrate data from external tables to normal tables. But the connection is always frozen half the way of executing script. The error message is ORA-00257. it looks redo log file is full. I tried to delete redo log file with RMAN, but I got this error message:
Sounds like you are confusing (online) redo logs with "archivelogs" (archived redo logs).
You don't delete redo logs at all. You can delete archivelogs with rman, which is what your command is trying to do. Do you ever backup the archivelogs? A proper backup/recovery policy would backup the archivelogs on at least a daily (if not more often) basis, and delete them after they are backed up. That will keep the archivelog destination from filling up in all but the most extreme circumstances.
delete archivelog until time 'trunc(sysdate)';
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=43 device type=DISK
specification does not match any archived log in the repository
Any suggestion would be appreciated.
Sam

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

Redo log file corupted, database not getting open

I am Oracle Funda-1 student.
Have install standard Oracle 9I on Windows XP pro service pack 2.
I made some changes in sample table & given commit. So log buffer will flush to redo log file.
Then I open current redo log file from OS & selected all junk characters [select all] & deleted same. Save the file. Causing redo file size 0KB.
Then made more changes to table & issue commit. no errors ! every thing working file.
Even chked V$log & V$logfile.
Again I open current redo log file from OS & selected all junk characters [ select all ] & deleted same. Save the file. Causing redo file size 0KB.
Then issue manual log switch. Alter system switch logfile
I got disconnected from database & database was close.
When I reconnected & try to open database in normal mode. Gave error saying redolog_1.log is corrupted & needed for recovery.
Now not even allowing me clear redo group 1. with alter database clear logfile group 1. as database is not coming to open stage.
just able to mount the database. with error rdolog_1 corrupted.
Wasn't oracle suppose to be halted when very 1st time I corrupted redo log file.
Why it disconnected me & got close.
When then one use alter database clear logfile group 1.

I may try this ALTER DATABASE OPEN RESETLOGS;
As no backup & not multiplex.
Still looking for explanation why database got close down instead of getting halt.
I have found one more status in V$log, which is not given in Oracle university book or online document.
INVALIDATED
Which come as a result when oracle unable to switch to next on line group due to non availability of next group redo log physical file.
SQL> select group#,members,status from V$log;
GROUP# MEMBERS STATUS
1 1 INVALIDATED
2 1 INACTIVE
4 1 UNUSED
As matter of fact, it's only portion of a big
document which happen to cover what you are testing
in detail.
I would invest time to read the document to
understand how things work instead of getting dirty
quick answers.

Removing Redo Log Files? What's Normal?

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