Question regarding PITR
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Thread: Question regarding PITR

  1. #1
    Join Date
    Dec 2000
    Posts
    138

    Question

    Hi,

    This one was already discussed yesterday, abt recovering a deleted row.

    The question I want to ask is , when getting the backup files If I copied the control files and redolog files also, it didnt work(or maybe I went wrong somewhere),
    But when i didnt copy the backed up control files, and redolog files it worked, why is it so and ofcourse I couldnt find this information in the documentation either.

    also, what is the difference between taking a copy of the control file as a backup and
    ALTER DATABASE BACKUP CONTROL FILE
    and
    ALTER DATABASE BACKUP CONTROL FILE TO TRACE .
    (I did a copy of the control file as backup for the above test).

    I'd appreciate any help.
    Thanks,
    -dharma.

  2. #2
    Join Date
    Feb 2002
    Location
    http://db-migration.co.in
    Posts
    50
    Hi
    First of All
    Backup control file is a binary backup of control file which can be read and interpreted by Oracle.
    Backup COntrol file to trace is the backup of control file in ASCII (text) mode so that one can edit the file to recreate the control file. (eg u can edit the control file to add/drop some parmeter, file, etc)

    Now, there is SCN # (system Change Number) generated by Oracle and written simultaneously to Control files, data files and Archived log files. When taking cold backup, the DB be shutdown (Shuldnot be Abort) and Physical copy of all the files. control files, data files, etc
    SO when one wants to restart the db with the backed up files, all the files (including datafiles have to be copied. Merely copying control files/RL files will not serve the purpose, as when DB starts, it cheks the SCN# in all the files and shud match. so all the files need to be copied
    (When u copy the file here, it shud be the binary control file and the trace file)
    feel free to ask if any further doubts



  3. #3
    Join Date
    Feb 2000
    Location
    Singapore
    Posts
    1,758
    SO when one wants to restart the db with the backed up files, all the files (including datafiles have to be copied. Merely copying control files/RL files will not serve the purpose, as when DB starts, it cheks the SCN# in all the files and shud match. so all the files need to be copied


    The above is true only if you are restoring from a COLDBACKUP.

    For PITR recovery...

    You restore your control file ONLY IF the current control files do not match the physical structure of the database at the intended time of recovery, restore a backup control file that reflects the database's physical file structure at the point at which incomplete media recovery should finish.

    In your case, you don't have to restore control file because you are only going to recover lost rows and the physical structure of the database remains unchanged.

    In HOTBACKUP you do not backup online redo log files. So there is no quesion of restoring redo log files. In case of any incomplete recovery you will have to open your db with RESETLOGS option.

    Sanjay


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