Redo log members in a group

Hi,
I am running 10gRac on Linux
I have 4 groups with 1 member each (50MB).
The DB is running in noarchive mode
I heard there is recommendation to have at least 2 members in each group.
Now how can I check if I should add more members to the groups?
Thanks

Hi br00klynZ00,
just imagine that you loose the only member of an unarchive group.
Maybe teh CURRENT?!
What do you do then?
You habe lost data then if you have a crash in addition because you cannot recover your lost instance.
So you should definitely have at least two members for each group!
=;-)
Hope this clarifies a little what the problem is.
BR,
Lutz

Similar Messages

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

    Hi All,
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    2)     copy log files from disk group 1 to disk group2 using RMAN (need to research on this)
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    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:
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    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

  • Writing in redo log members

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    >>> I had a 2 log groups with 2 members in each. how LGWR writes into log members of each group. whether it will done in serial(sequential order) or parallel? If it is sequential, when LGWR writes into 2nd member of one group if i perform a log switch, will it wait till it completes writing into that member and switches to another group?
    Mr.Howard Rodger wrote:-
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    Regards
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    Thanks

    user12020966 wrote:
    Hi,
    I have problem with one of the redo log file i issued the ALTER DATABASE CLEAR LOGFILE GROUP 3; command. the status right now is clearing since last some hours.
    Can i create new redo log and assign to group 3. will the status will be inactive or active? how to add redo log and group please explain!
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  • Filling of redo log members

    Hello!
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    Pavel wrote:
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    For example, on exadata, redo can be written to both SSD and hard disk, and whichever is done first is sync, and the other isn't.
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  • Redo Log Members & RAID 5

    Hi,
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    For example here:
    http://asktom.oracle.com/pls/ask/f?p=4950:8:::::F4950_P8_DISPLAYID:359617936136
    Try search google btw. There are plenty of articles.
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    See a recent discussion on this issue :
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  • Dropping Redo Log Members

    hi
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    The link is :
    http://download.oracle.com/docs/cd/B28359_01/server.111/b28310/onlineredo005.htm
    Thanks

    >
    but i tried it in Oracle's Database 10g and it's dropped successfully >
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    Refer to the link for the status of the redo logs [http://download.oracle.com/docs/cd/B14117_01/server.101/b10755/dynviews_1126.htm#REFRN30127]
    23:36:05 venture >select * from v$log;
        GROUP#    THREAD#  SEQUENCE#      BYTES    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM
             1          1         29  104857600          1 NO  INACTIVE               7457724 07-DEC-08
             2          1         30  104857600          1 NO  INACTIVE               7794484 08-DEC-08
             3          1         33  104857600          1 NO  CURRENT                8016830 09-DEC-08
             4          1         31  104857600          1 NO  INACTIVE               8016825 09-DEC-08
             5          1         32  104857600          1 NO  INACTIVE               8016827 09-DEC-08
    23:38:01 venture >create table test as select rownum id,'TEST' name from dual connect by level <= 10000000;
    Table created.
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    23:39:27 venture >select * from v$log;
        GROUP#    THREAD#  SEQUENCE#      BYTES    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM
             1          1         29  104857600          1 NO  INACTIVE               7457724 07-DEC-08
             2          1         30  104857600          1 NO  INACTIVE               7794484 08-DEC-08
             3          1         33  104857600          1 NO  CURRENT                8016830 09-DEC-08
             4          1         31  104857600          1 NO  INACTIVE               8016825 09-DEC-08
             5          1         32  104857600          1 NO  INACTIVE               8016827 09-DEC-08
    Elapsed: 00:00:00.00
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    ERROR at line 1:
    ORA-01623: log 3 is current log for thread 1 - cannot drop
    ORA-00312: online log 3 thread 1: 'D:\ORACLE\ORADATA\VENTURE\REDO03.LOG'
    Elapsed: 00:00:00.01
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    System altered.
    Elapsed: 00:00:00.01
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             1          1         34  104857600          1 NO  CURRENT                8017910 09-DEC-08
             2          1         30  104857600          1 NO  INACTIVE               7794484 08-DEC-08
             3          1         33  104857600          1 NO  ACTIVE                 8016830 09-DEC-08
             4          1         31  104857600          1 NO  INACTIVE               8016825 09-DEC-08
             5          1         32  104857600          1 NO  INACTIVE               8016827 09-DEC-08
    Elapsed: 00:00:00.00
    23:40:03 venture >alter database drop logfile group 3;
    alter database drop logfile group 3
    ERROR at line 1:
    ORA-01624: log 3 needed for crash recovery of thread 1
    ORA-00312: online log 3 thread 1: 'D:\ORACLE\ORADATA\VENTURE\REDO03.LOG'
    Elapsed: 00:00:00.00
    23:40:11 venture >alter system switch logfile;
    System altered.
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    23:40:25 venture >select * from v$log;
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             1          1         34  104857600          1 NO  INACTIVE               8017910 09-DEC-08
             2          1         35  104857600          1 NO  CURRENT                8018022 09-DEC-08
             3          1         33  104857600          1 NO  INACTIVE               8016830 09-DEC-08
             4          1         31  104857600          1 NO  INACTIVE               8016825 09-DEC-08
             5          1         32  104857600          1 NO  INACTIVE               8016827 09-DEC-08
    Elapsed: 00:00:00.00
    23:40:28 venture >alter database drop logfile group 3;
    Database altered.
    Elapsed: 00:00:00.00
    23:40:42 venture >select * from v$log;
        GROUP#    THREAD#  SEQUENCE#      BYTES    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM
             1          1         34  104857600          1 NO  INACTIVE               8017910 09-DEC-08
             2          1         35  104857600          1 NO  CURRENT                8018022 09-DEC-08
             4          1         31  104857600          1 NO  INACTIVE               8016825 09-DEC-08
             5          1         32  104857600          1 NO  INACTIVE               8016827 09-DEC-08
    Elapsed: 00:00:00.00
    23:40:46 venture >HTH
    Anand

  • REDO Log Members

    Hello-
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    Thanks-

    Admin. Guide says http://download.oracle.com/docs/cd/E11882_01/server.112/e17120/onlineredo002.htm#ADMIN11309
    >
    To protect against a failure involving the redo log itself, Oracle Database allows a multiplexed redo log, meaning that two or more identical copies of the redo log can be automatically maintained in separate locations. For the most benefit, these locations should be on separate disks. Even if all copies of the redo log are on the same disk, however, the redundancy can help protect against I/O errors, file corruption, and so on.

  • Larger redo log file members or more log groups

    Oracle 11gR1 RHEL5 64 bit
    Hi,
    I was wondering what is better from a perfomance tuning perspective. I have log swiches occuring every 2 minutes in our production database. I know definitely that our log file members are too small (100MB). The redo log sizing tool in OEM told me to make it 40G according to the fast_start_mttr_target setting which is set to 600. Now, my question is what is better to do?
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    If you want to reduce the number (frequency) of Log Switches, you should increase the size of the Online Redo Logs -- ie create new Log File Groups of a larger size and drop the older ones.
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    Hemant K Chitale
    http://hemantoracledba.blogspot.com

  • Online Redo Log groups

    Dear All,
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    Further in which situation we will add Online Redo Log Groups and which situation we will add Log Members.
    My rollback segment is using System tablespace is it recommended?
    What is recommendation about 1 redo log group is redo log member or 1 redo log group is multiple redo log members.

    Thanks Mr. Nicolas. for your informative guidence.
    Can I check how much time my redo log file data have been overwritten?Check v$loghist.
    We have 218 records in v$loghist, it means 218 times data have been overwritten, i think its not good. Can you guide me how to rectyify this.
    in which situation we will add Online Redo Log GroupsIn case of checkpoint not complete reported into alert.log.
    How to findout checkpoint entry in alert.log
    which situation we will add Log Members.This is the redolog multiplexing, at least two members for each redolog group.
    Ok, Can we do multiplexing for members or just do for groups.
    My rollback segment is using System tablespace is it recommended?No.
    OK, can we change rollback segments tablespace.
    1 redo log group is redo log member or 1 redo log group is multiple redo log membersA minimum of two redolog group with two members for each.
    After, it depend of your db activity.
    We have just one member for each group and we have three groups, so whats ur recommnedation we will add 1 member in each group.

  • Log members per log group

    Apologies in advance if this has been answered already, I did try to find the answer first.
    Is a log group in a data warehouse meant to have more than one member per group? That is, if there are three log groups, is there meant to be three (or, for example six) log members?
    Also, what does it mean if one of the log members are not the same size as the others (as reported in a Toad health check)?

    A Redo Log group consists of redo logfiles called members that saves the identical information. These redo log members can only belong ot single redo log group.
    Is a log group in a data warehouse meant to have more than one member per group?Good idea is to have 3 redolog groups with two members each.
    Cheers, Bhupinder

  • What will heppen if redo logs at os level get deleted

    Friends,
    need 1 answer about the query: what will heppen if redo logs at os level get deleted.

    how can i find where are my multiplexed redo logs, so that i can copy it from there
    SQL> shutdown abort                       
    ORACLE instance shut down.                
    SQL> startup mount                        
    ORACLE instance started.                  
    Total System Global Area  534462464 bytes 
    Fixed Size                  2256912 bytes 
    Variable Size             398462960 bytes 
    Database Buffers          125829120 bytes 
    Redo Buffers                7913472 bytes 
    Database mounted.                         
    SQL> select * from v$logfile              
      2  ;                                    
        GROUP# STATUS  TYPE                   
    MEMBER                                    
    IS_                                       
             3         ONLINE                 
    C:\O\ORADATA\XE\REDO03.LOG                
    NO                                        
             2         ONLINE                 
    C:\O\ORADATA\XE\REDO02.LOG                
    NO                                        
        GROUP# STATUS  TYPE                   
    MEMBER                                    
    IS_                                       
             1         ONLINE                 
    C:\O\ORADATA\XE\REDO01.LOG                
    NO                                         However, Oracle knows about the multiplexing, so if your logs were multiplexed properly (using redo log members), Oracle would already have known about them and identified that there was one available.
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  • Redo log files deleted

    Hello,
    One of my friend deleted redo log and control files of one machine in cluster environment. Oracle parallel server(8.1.7) is installed on this cluster.
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    Can i copy the control files and redo log files of the second disk to the first one...??? Will it work ???
    Please let me know how should I go by it...??
    Thanking in anticipation.
    Regards,
    Rajeev

    Hello,
    I don't have any experiences with cluster/parallel server. But in general:
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    2. Redo Logs: Drop and recreate groups step by step (no user activity recommended). Database won't crash, because members are still "alive" on second disk.
    HTH,
    juergen_klinsmann

  • How does LGWR write  redo log files, I am puzzled!

    The document says:
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    my undestandint of the sentence is following for example
    group a includes file(a1, a2)
    group b includes file(b1, b2)
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    my question is following:
    1、 my understanding is right?
    2、 if my understanding is right, I think that separate log file in a group should save in different disk. if not, it cann't guarantee correctly recovery.
    my opinion is right?
    thanks everyone!

    Hi,
    >>That is multplexing...you should always have members of a log file in more than 1 disk
    Exactly. You can keep multiple copies of the online redo log file to safeguard against damage to these files. When multiplexing online redo log files, LGWR concurrently writes the same redo log information to multiple identical online redo log files, thereby eliminating a single point of redo log failure. In addition, when multiplexing redo log files, it is preferable to keep the members of a group on different disks, so that one disk failure will not affect the continuing operation of the database. If LGWR can write to at least one member of the group, database operation proceeds as normal.
    Cheers
    Legatti

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