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Backups too slow and too large

Discussion in 'Security, Backup and Recovery' started by AMINE DBA, Oct 22, 2018.

  1. AMINE DBA

    AMINE DBA Newly Initiated

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    Hi,
    I administer a database (on AIX) with a size of more than 3T
    compressed backups in disks are larger than 600G and take longer than 8h
    I can not find the problem, how to reduce the backup time?
     
  2. myankitx

    myankitx Newly Initiated

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    use channels for diff act in rman bkp it would assist
     
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  3. zargon

    zargon Community Moderator Forum Guru

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    The first 'problem' is expecting a 3+ TB database to back up in less than 8 hours. Most take 8 to 10 hours for a complete backup. If you're not on SSD that would also be a 'problem' as standard disks have a higher latency than SSD.
     
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  4. zargon

    zargon Community Moderator Forum Guru

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    Please explain that response.
     
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  5. myankitx

    myankitx Newly Initiated

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    You can allocate up to 255 channels; each channel can read up to 64 files in parallel. You can control the degree of parallelism within a job by the number of channels that you allocate. Allocating multiple channels simultaneously allows a single job to read or write multiple backup sets or disk copies in parallel, which each channel operating on a separate backup set or copy.

    When making backups to disk, the guideline is to allocate one channel for each output device (see Example 2-7). If RMAN is writing to a striped file system or an ASM disk group, however, then multiple channels can improve performance. When backing up to tape, the guideline is that the number of tape channels should equal the number of tape devices divided by the number of duplexed copies
     
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  6. myankitx

    myankitx Newly Initiated

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    Example 2-7 Distributing a Backup Across Multiple Disks

    SET BACKUP COPIES command to indicate that RMAN should create two identical copies of the database backup. Because the guideline is that the number of tape channels should equal the number of tape devices divided by the number of duplexed copies, you allocate two channels. In this case the BACKUP_TAPE_IO_SLAVES initialization parameter must be set to TRUE.

    In the OB_DEVICE_n parameter for Oracle Secure Backup, the n specifies the copy number of the backup piece. RMAN writes copy 1 of each backup piece to tape drives stape1 and stape2 and writes copy 2 of each backup piece to drives stape3 and stape4. Thus, each copy of the database backup is distributed between two tape drives, so that part of the data is on each drive.

    RUN
    {
    ALLOCATE CHANNEL t1 DEVICE TYPE sbt
    PARMS 'ENV=(OB_DEVICE_1=stape1,OB_DEVICE_2=stape3)';
    ALLOCATE CHANNEL t2 DEVICE TYPE sbt
    PARMS 'ENV=(OB_DEVICE_1=stape2,OB_DEVICE_2=stape4)';
    SET BACKUP COPIES 2;
    BACKUP DATABASE;
    }
     
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  7. zargon

    zargon Community Moderator Forum Guru

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    You can copy text from the documentation; why didn't you explain this in your OWN words? THAT would have been much more helpful to others.

    How much Oracle administration experience do you have?