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  1. #1
    Join Date
    May 2011
    Posts
    2

    Smile Unanswered: db2 backups very slow

    Hi, I have 4 TB db2 db. all tablespaces complete very fast except one tablespace PSAPBTABD (2 terra byte )

    ** This tablespace takes 36 hours to completes
    ** The start backup throughput is 100MB / second which is good
    ** after 3 hours the backup throghput falls down to 10MB / sec which is bad

    We have tried the following:

    ** Increase utility memory
    ** rebalance the PSAPBTABD from one stripe set to 10 stripe sets
    ** Increase the DB2_PARALLEL_IO=*:5
    ** Upgrade the DB2 9.1 to latest fix pak 10

    Nothing works, this tablespace is very slow, all other small tablespaces take good backup throughput of 100mb/sec. We have called in the TSM tivoli vendor. He confirmed there is no issue with TSM layer

    Anyone has any thoughts?

    Thanks in advance...

  2. #2
    Join Date
    May 2003
    Location
    USA
    Posts
    5,737
    Specify multiple paths for the backup, preferably on different disks or different disk arrays (each with its own mount point). For example:

    backup db sample to /db2/backup1/sample, /db2/backup2/sample, /db2/backup3/sample, /db2/backup4/sample compress
    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
    Join Date
    May 2011
    Posts
    2
    Hi, I am using TSM with 4 sessions, also tried with 8 sessions and parallelism 16.

    The initial 20% of the backup goes very fast and after that It slows down and takes 36 hours

  4. #4
    Join Date
    Jan 2010
    Posts
    335
    Quote Originally Posted by mbuhari View Post
    ** rebalance the PSAPBTABD from one stripe set to 10 stripe sets
    What do you mean by stripe set? You have 10 Containers for the TBS? Or do you have a single LUN build from 10 Stripe Sets from your SAN?

    100 MB/s is compressed or not? If it's uncompressed, i'ld guess there's a bottleneck somewhere (network???). But that's more general and not related with the backup of your tablespace.

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