7 Replies Latest reply: Jan 23, 2014 10:50 PM by Hemant K Chitale RSS

RMAN incremental backup from scn to scn

AnandKumar Newbie
Currently Being Moderated

Hi All

 

Oracle Version -11.2.0.3 EE

OS - Linux 5L

 

Recently we faced missing archives in PROD and bcos of this the standby is not sync. Hence decided to do RMAN incremental backup (from SCN (last SCN of DR db) and did it successfully. My question is; is there a command "from SCN  XXX to SCN XXX" while doing incremental backup. I initally searched in google and got hits for "from sequence  XXX to Ssequence  XXX" and not for SCN.

 

Why this question is we had only 3 days archives missing (say Jan 10 to 13) other archives are present (jan 14 to current). If "from SCN  XXX to SCN XXX" exists; we can reduce the manual transfer of RMAN files from Prod to DR as we can transfer only 3 days archives (inc backup);

 

Regards

Anand

  • 1. Re: RMAN incremental backup from scn to scn
    Baris Yildirim Guru
    Currently Being Moderated

    Hi,

     

    "from SCN  XXX to SCN XXX"

     

    How can it be possible?

     

    No it's impossible

     

    Regards

  • 2. Re: RMAN incremental backup from scn to scn
    AnandKumar Newbie
    Currently Being Moderated

    Can you technically clarify me ...

  • 3. Re: RMAN incremental backup from scn to scn
    Baris Yildirim Guru
    Currently Being Moderated

    Hi,

     

     

    The system change number (SCN) is an ever-increasing value that uniquely identifies a committed version of the database. Every time a user commits a transaction,

    Oracle records a new SCN. Oracle uses SCNs in control files, datafile headers, and redo records.

     

    You want to backup FROM SCN........TO SCN,

         FROM SCN is OK, but TO SCN which doesn't exists anymore in your database.

     

    Regards

  • 4. Re: RMAN incremental backup from scn to scn
    Levi-Pereira Guru
    Currently Being Moderated

    Please clarify this:


    Why this question is we had only 3 days archives missing (say Jan 10 to 13) other archives are present (jan 14 to current). If "from SCN  XXX to SCN XXX" exists; we can reduce the manual transfer of RMAN files from Prod to DR as we can transfer only 3 days archives (inc backup);

     

    You are trying to restore:

    1) A Full backup taken before  Jan 10  ?

    2) Are missing archivelog Jan 10 to Jan 13, and you are trying bypass these days using "from SNC xxx to SCN xxx"?

    3) What is the timestamp or SNC which you are trying to get?


    Please also post, backup full from timestamp/snc xxxx and trying to recovery database until timestamp or snc xxx.



  • 5. Re: RMAN incremental backup from scn to scn
    Hemant K Chitale Oracle ACE
    Currently Being Moderated

    The source production database is constantly being updated.  Say at 10:00 am the highest SCN was 1001 and at 5pm the highest SCN was 2045. Can you do a backup FROM SCN x TO SCN 2040 ?  (x may be 950 or 1050, it doesn't matter). Some database blocks have been updated to a higher SCN than 2040.

     

    You cannot have a TO SCN backup.

     

     

    Hemant K Chitale


  • 6. Re: RMAN incremental backup from scn to scn
    AnandKumar Newbie
    Currently Being Moderated

    Thanks Hemant for your reply.

    Consider the following,

    • Standby DB last SCN say 146 (after that no recovery as archive logs are missing).
    • We are taking inc backup from SCN 146 in prod.
    • Current SCN in prod is say 500. (while taking backup, after this SCN moves on in prod)
    • After recover with noredo in standby, the SCN of standby points to the SCN in the incremental backup (i.e 500).

     

    So ideally, i am recovering the standby from scn 146 to scn 500. and after that normal standby RFS and MRP comes into picture.

     

    So this (from scn to scn ) is technically possible, but no command exists for this from ORACLE.

    Please correct me if i am wrong.

     

    Regards,

    Anand.

  • 7. Re: RMAN incremental backup from scn to scn
    Hemant K Chitale Oracle ACE
    Currently Being Moderated

    When you run the backup of the primary, some database blocks are backed up at SCN 147, some are backed up at SCN 500.

    In between the two, some blocks may get backed up when their SCN is 200 but, after they are backed up and before the last block backup in that databse, those same blocks might get updated to SCN 495.

    So recovery wouldn't be from SCN500.  IT could be from SCN 147 or it could be from SCN 200 or it could be from SCN 495.

    Oracle checks the datafile header to find the datafile  checkpoint SCN and takes that as the lowest SCN in each datafile -- some blocks are at an SCN higher than the datafile header checkpoint information !

     

    Hemant K Chitale

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