How to Mirror Control Files and Control File Review
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Thread: How to Mirror Control Files and Control File Review

  1. #1
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    How to Mirror Control Files and Control File Review

    Oracle 8.16, Windows 2000.

    I know I should mirror my control files. Can someone please explain to me how to proceed with this process or are the control files mirrored automatically? If they are mirrored automatically where are the mirrored images located. I've attached a snippet of my init file.
    control_files =("D:\Oracle8i\oradata\PROD\control01.ctl", "D:\Oracle8i\oradata\PROD\
    control02.ctl", "D:\Oracle8i\oradata\PROD\control03.ctl")

    Also, it appears that my control files are all located on the same disk. I believe I should copy these files and move them to another disk. Am I correct in my assumption?

    I have read the 8i admin guide section concerning Managing Control Files, and I've looked at the O'Reilly Oracle Database Administration book. I can't find any specific information concerning the mirroring of the control files.

    Thanks in advance
    BradO

  2. #2
    Join Date
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    shutdown your database,
    then copy existing control file to your new destinations,
    update init/spfile and
    startup your database.

  3. #3
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    yes they should be on different disks, if you lose the disk you lose of you files, in your case you might as well only have one (except Oracle wouldnt allow it).

    Bet all your datafile are on the same disk as well

    So yeah, copy one onto other disk and the third onto a third disk
    should be pretty safe then.

  4. #4
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    Originally posted by davey23uk
    (except Oracle wouldnt allow it)
    Why not? Oracle will have absolutely nothing against a setup with only one control file (but your boss might, after you've lost the only copy of it).
    Jurij Modic
    ASCII a stupid question, get a stupid ANSI
    24 hours in a day .... 24 beer in a case .... coincidence?

  5. #5
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    Thought Id add my 10 pence worth.

    It is VERY important to mirror your controlfiles on totally separate physical disks, and it is SO easy to do (as sysdba said):

    shutdown the database
    physically copy (dont move it) the controlfile to a new location.
    point the init.ora at it (add it to the control_files parameter)
    start up your database again. piece of cake!

    If you only have one controlfile and the disk it is on dies - you have no choice but to perform incomplete recovery......

    Mark
    --------------------------------
    Mark Backhouse
    Oracle Database Administrator
    Great North Eastern Railways
    York
    UK

  6. #6
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    Originally posted by markbackhouse
    If you only have one controlfile and the disk it is on dies - you have no choice but to perform incomplete recovery......
    Incomplete recovery? Why? There is nothing that prevents you from performing complete recovery in such a situation.
    Jurij Modic
    ASCII a stupid question, get a stupid ANSI
    24 hours in a day .... 24 beer in a case .... coincidence?

  7. #7
    Join Date
    May 2003
    Location
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    D'oh! sorry my fault - wasn't thinking clearly!

    You either have to recover using a backup of the controlfile or re-create it so ok it is complete recovery (with reset logs). Think when I posted this must have confused myself with a scenario we had a while back in my last job with loss of control file but it was complicated with loss of redo logs also.....
    --------------------------------
    Mark Backhouse
    Oracle Database Administrator
    Great North Eastern Railways
    York
    UK

  8. #8
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    Sep 2002
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    Thanks for the information. Just to clarify, mirroring simply refers to having copies of the control files on different disks? I truly do understand the importance of having copies of the control files I just want clear up the exact definition of mirroring.
    BradO

  9. #9
    Join Date
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    Location
    York, UK
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    yeah, it simply means to have more than one phyiscal copy of the control file referenced in the init.ora control_files parameter. Having the different copies on totally separate disks is the recommended way to mirror control files and redo logs but you are not forced to put them on separate disks at all it just makes sense to.
    --------------------------------
    Mark Backhouse
    Oracle Database Administrator
    Great North Eastern Railways
    York
    UK

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