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  1. #1
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    Unanswered: DB2 backup question on AIX

    I have a DB2 database backup I create every night. It is a full backup to disk images. Here is the command:

    db2 backup database 'PR1' TO '/bk01,/bk02,/bk03' WITH '6' BUFFERS BUFFER '2048' PARALLELISM '6'

    Well, '/bk01' .. '/bk03' are 3 journaled filesystems that are 113GB each.

    Every night, I get 1 or 2 of these filled, while the third one has 10GB free.

    On my other system, which has identical filesystems, only called '/dv01' ... '/dv03' we do a backup with the same command, except 'PR1' is replaced by 'DV1' and the filesystems are allocated much more evenly.

    My host machine for both backups is a RS/6000 H80 with 6 processors and 8GB of memory.

    Can anyone offer any thoughts on this ?

    Thanks, Bill.

  2. #2
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    I believe that specifying multiple directories causes the backup to be done in parallel to the specified locations, at the tablespace level. This is not the same as if each tablespace is striped across all the directories (the way it works with multiple tablespace containers). So if the tablespace sizes are not the same on each database, this could cause the sizes to be unbalanced.
    M. A. Feldman
    IBM Certified DBA on DB2 for Linux, UNIX, and Windows
    IBM Certified DBA on DB2 for z/OS and OS/390

  3. #3
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    Originally posted by Marcus_A
    I believe that specifying multiple directories causes the backup to be done in parallel to the specified locations, at the tablespace level. This is not the same as if each tablespace is striped across all the directories (the way it works with multiple tablespace containers). So if the tablespace sizes are not the same on each database, this could cause the sizes to be unbalanced.
    I see your point.

    The database instances are roughly the same. Filesystem names are identical, however the "PR1" database is about 13GB larger. But table names are identical - just larger.

    I am just perplexed that the 2 'bk' filesystems literally fill up to 100% used and the last one is only ~90% used, whereas the 'dv' filesystems are all in the 90% range. They seem to balance more.

    Thanks- Bill.

  4. #4
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    Do you know what happens if the file systems are different sizes. Does the backup fully utilize all the space even if they are different sizes?
    M. A. Feldman
    IBM Certified DBA on DB2 for Linux, UNIX, and Windows
    IBM Certified DBA on DB2 for z/OS and OS/390

  5. #5
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    Originally posted by Marcus_A
    Do you know what happens if the file systems are different sizes. Does the backup fully utilize all the space even if they are different sizes?
    The other admin just made a discovery...the filesystems are all striped I knew that much). However, the stripe size on the 'bk' filesystems is larger than the 'dv' filesystems. I'm going to re-create the 'bk' filesystems with the smaller stripe size then post the results tomorrow after tonight's backup.

    Thanks for everything.

    BV

  6. #6
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    Originally posted by bjverzal
    The other admin just made a discovery...the filesystems are all striped I knew that much). However, the stripe size on the 'bk' filesystems is larger than the 'dv' filesystems. I'm going to re-create the 'bk' filesystems with the smaller stripe size then post the results tomorrow after tonight's backup.

    Thanks for everything.

    BV
    When I corrected the disk striping parameters, my problem was resolved. Thanks to everyone.

    BV

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