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Former Member

online back v/s offline back up

hi experts

i used to take whole offline backup+redolog backup configured through BRTOOLS

but as we purchased HP DATA PROTECTOR license also and now our HP hardware and software engineer asking to take

online backup only and advice me to take offline back up onece in a month.

i just want to confirm that is this whole database online + redolog backup is safe

and will it make my system down while taking backup or does it make the performance down

or i will continue to take whole offline + redolog backup

which one is best please advice.

regards

Aditya Rathore

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5 Answers

  • Best Answer
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    Former Member
    Nov 17, 2009 at 11:57 AM

    Hello,

    Here's a summary which I hope will help you:

    Backup

    Online backup leaves the database fully available for all normal activity, both reading and writing. However, database writing will take a performance hit (unless the backup is done with Oracle RMAN).

    It is good practice to do a daily online backup of your database. Schedule this backup at a time of relatively low activity. It is often not a good idea to do the online backup in the middle of the night because of concurrent background processing, which often does a lot of database writes.

    Online backup is only possible if the database is in ARCHIVELOG mode. For SAP production systems this is mandatory anyway.

    During offline backup the database is unavailable (obviously). After restarting the database there will again be a performance hit because the Oracle data buffer and shared pool have to be gradually rebuilt. When you take an offline backup, stop the database but leave the SAP instance running. This will at least leave the memory buffers of SAP intact, otherwise the performance hit could be quite hard. The 'database reconnect' feature of the SAP kernel will ensure that the instance can connect to the database and continue working after you have restarted the DB.

    Offline backups are possible also for databases in NOARCHIVELOG mode (but running an SAP database in noarchivelog is never a good idea).

    Do you need offline backups? Technically no: it is perfectly possible to have a backup schedule based only on online backups. However most SAP sites prefer to have an occasional offline backup, e.g. weekly (if a downtime window is available for that). SAP does not require you to make any offline backups.

    Restore

    An offline backup is consistent in itself, so you can restore it without recovering archive logs. An online backup is not usable without at least the archive logs created during the backup.

    This means that technically restoring from an offline backup is easier, but in reality that does not really play a role. If you take an offline backup say every Sunday and the system crashes on Monday afternoon, you will not want to return to the state of the database on Sunday; you want to apply all archive logs between the backup and the time of the crash so as to have zero data loss. The only case where an offline backup is more convenient is when you use it to refresh a copy of the production system (e.g. periodic refresh of your QA environment).

    Regards,

    Mark

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  • Nov 14, 2009 at 07:14 AM

    HI.. Aditya

    If you get the down time daily during the offline backup then it is good take a offline backup,

    else your online+redo which also a consitent backup, you can schedule daily via your HP Data protector,

    It depends on the business criticality.

    and also check how to restore from HP Data Protector,

    and how you are planning to take offline backup using HP Dataprotector or using BRTOOLS

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    Former Member
    Nov 14, 2009 at 08:55 AM

    Hi Rathore,

    Online/Offline backup purely depends upon your business requirement/commitment.

    As HP DATA Protector will take onlin/offline backup consistantly....which means you can take daily online+redolog backup and whenever you get downtime for your business then you can perform offline backup.

    But during online backup performance would be very slow...and i recommend you to schedule the same during non peak hours.

    with online backup also you can recover your database....

    Regards

    Nick Loy

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    Former Member
    Nov 16, 2009 at 04:56 AM

    Hi Rathor,

    If you have the chance to take offline everyday...then anyone can prefer to restore offline.

    If you are restoring offline backup, then there is no need to recover your database with archivelogs.

    In restoring online backup, you need to recover your database with applying archive logs.

    Regards

    Nick Loy

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    Former Member
    Nov 16, 2009 at 07:45 AM

    Hi Aditya,

    Yes take online daily backup & Mon to Saturday & Sunday Offline backup. which is standard schedule of backup in most of companies.

    Online backup word itself explains your system is online & working during Backup too. Sunday is holyday so no problem to tack down time for offline backup.

    BR,

    Darshan

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