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Crash consistent backups

We create snapshots(known as replays on the Compellent disk array) on our local SAN and then replicate these snapshots to our DR SAN. These snapshots contain all SAP and Oracle file systems. The snapshots are created while SAP and Oracle are up and running.

We have tested these snapshots and we were able mount these snapshots on a different server and the instance came up.

We also tested these snapshots where we mounted the snapshots of all the sapdata directories from time N and then mounted the snapshots of the directories of the online and offline redolog files  and the control file from time N+t where t>0 and then recovered using the command: RECOVER AUTOMATIC DATABASE. We were able to recover to time N+t.

I was wondering if somebody is using this "Crash Consistent" recovery and if there are any comments or suggestion that some may have.

Thanks.

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3 Answers

  • avatar image
    Former Member
    Feb 26, 2013 at 07:48 PM

    Hello Jamal,

    In my optinion you have it all already.

    The most important when defining a backup strategy is to chose the option that fits better your case and perform restore tests with a frequency. I'd say at least once a quarter.

    I see you have already done these steps.

    Best regards,

    Thiago

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    Former Member
    Feb 27, 2013 at 06:25 AM

    Hi Janal,

    >> The snapshots are created while SAP and Oracle are up and running.

    The tablespaces are in the backup mode while creating the snapshots, isn't it?

    Because all the configurations and files have been backed up in the snapshot, it will work properly. The problem may arise just only when you restore a single file from the snapshot, such as an offline redolog file. Many devices support this feature, but to be safe side check this option on your device.

    Best regards,

    Orkun Gedik

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    • Former Member Jamal Asi

      Hi,

      Under normal conditions, the database should be in the backup mode during the online backup, as I noted in my previous message. I heard that Oracle supports some of the storage vendors consistent crash recovery solution without hot backup mode, such as EMC or NetApp.

      Additionally, RMAN support this feature, as noted in the SAP note, below on item 53;

      Note 105047 - Support for Oracle functions in the SAP environment

      In this case, I suggest you contact to your storage vendor, to learn support on online backup without hot backup mode.

      Best regards,

      Orkun Gedik

  • Feb 27, 2013 at 09:51 PM

    Hi,

    in my opinion you lack a couple of things

    (which you might in fact perhaps do, but did not write them here).

    Are you doing anything around the snapshots?

    Like "begin backup" / "end backup" or any kind of suspending writes

    in a consistent manner accross all filesystems involved?

    (i.e. snapmounting oraarch while a redolog is half way written is a bad idea)

    In addidtion, check this

    http://www.oracle.com/technetwork/database/features/availability/rman-fra-snapshot-322251.html

    Volker

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    • Former Member Jamal Asi

      Hi Jamal,

      Thanks for the information.

      Yes, this is something that you need validation from your SAN vendor. This is a backup method that's not supported by SAP, even though it is permitted.

      By as I said earlier, for maintaining a backup strategy all you need to do is test it frequently to make sure it is consistent. Also avoid any issues in case you have a crash and need to use it. It is good to have a document to guide on the restore process as well.

      Best regards,

      Thiago