How to multiplex redo logs?
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Thread: How to multiplex redo logs?

  1. #1
    Join Date
    Oct 2000
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    What are the exact steps to multiplex the current group of online redo logs to another disk? For example, we currently just have 1 group of redo logs with 10 members. How do I create another group of redo logs on another disk that are exact mirrors of the existing logs? Also, can the database be open to do this or should it just be mounted?

    Thanks in advance!

  2. #2
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    Thanx
    Sam



    Life is a journey, not a destination!


  3. #3
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    Oct 2000
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    Yeah, I had already looked at that from the Administrator's Guide, but this is a large production database and I wanted to verify the steps so to make sure I don't screw anything up. Just so I know, with the database up (?), I just do:

    svrmgrl> alter database add logfile group 2 ('/database/redo2/log1.rdo', '/database/redo2/log2.rdo', ... '/database/redo2/log10.rdo') size 25M;

    I guess it just seems to easy, which is why I posted this question. Is there anything else I need to do?

    Thanks again.

  4. #4
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    Oct 2000
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    Nope, what I said above is not right. After consulting yet another book, I *think* I halfway understand mirrored redo logs. As I stated before I have 10 redo logs that are apparently already assigned group #1... group #10 (checked v$log). So to mirror the first log I would do 'alter database add logfile group 1 ('/database/redo2/log1.rdo') size 25M', and to mirror the second log I would do 'alter database add logfile group 2 ('/database/redo2/log2.rdo') size 25M'. My statement above was basically trying to "mirror" the group 2 redo log 10 times, even worse on the same disk.

    If I am wrong about this somebody please tell me. I can't be the only one confused about groups and members.

    [Edited by lake612 on 05-08-2001 at 08:18 AM]

  5. #5
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    You should have at least 2 groups of redo logs to work with Oracle.
    Each group can have one or more members. It's recommended to have at least 2 members in each group.

    Oracle writes redo information to each member of the current group. If one of the members goes bad (deleted, corrupted, inaccessible), Oracle will still work if it can write to at least one of the members of that group.

    I guess in your case you have 10 groups with one member each (no multiplexing) and what you need to do is add members to your existing groups.

    select * from v$log;

    will show you how many groups you have (group# column) and how many members in those groups each (members column).

    If this is the case then you should do as following --

    If you have a group (say group 1) with just 1 member setup like --

    'C:\ORACLE\ORADATA\DBA1\REDO11.LOG

    Then you should do --

    ALTER DATABASE ADD LOGFILE MEMBER 'C:\ORACLE\ORADATA\DBA1\REDO12.LOG' TO GROUP 1

    This will add another member in that group. You can add as many members as you want. The file name should be different for each member.

    You don't need to specify the size of the member; It will be picked from the size of the first member because all the members must be of same size.

    Please let us know if this is not clear yet.

    - Rajeev


    You may

    Rajeev Suri

  6. #6
    Join Date
    Oct 2000
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    Thanks Rsuri for your detailed answer! It was very helpful. I think I'm clear on this now

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