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Slow running backup

  • 1.  Slow running backup

    Posted Fri June 19, 2020 01:24 AM
    Hello everyone,

                If the backup is running slow thru ontape command , how can we check that and what could be the reason for slow backup?
    And what could be the resolution?

    Thanks
    Amit Patel

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    AMIT PATEL
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  • 2.  RE: Slow running backup

    Posted Fri June 19, 2020 08:30 AM
    Amit:

    You can check the progress of archives by zeroing out stats at the beginning of the archive (onstat -z) then monitoring the reads with onstat -D where you can see the heavy read activity slide from one chunk to another dbspace by dbspace.

    As to causes, heavy update activity can increase activity in the physical log. Pages written there have to be copied to temp tables (one for each dbspace) until the dbspace associated with each is completed and the temp table contents are pushed out to the archive. So, the more update activity the more extra IO for physical log pages. In addition high disk activity will slow the reads the archive needs. Beyond that, contention for the chunk drives and/or archive target from other applications not related to the database and the archive will have an effect. If you are archiving across the network then network contention will also affect performance.

    Art

    Art S. Kagel, President and Principal Consultant
    ASK Database Management


    Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference.  Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves.








  • 3.  RE: Slow running backup

    Posted Fri June 19, 2020 10:06 AM

    variety of reasons.

     

    a very simple test will be to take a level 0 archive to /dev/null.  If the time is still slow then its probably due to  either a lot of database activity or i/o transfer rate back from the storage where the db chunks reside. If fast then it's the transfer rate to the backup device that's probably the root cause.

     

    Then again if your backing up to nas device then there is the network to consider.

     

     

    you can use onstat -g stq to monitor the archive stream queue buffers. See the below link for more info.

     

    https://www.ibm.com/support/pages/node/548407

     






  • 4.  RE: Slow running backup

    Posted Mon June 22, 2020 02:32 AM
    You can try 'dd' command to see the IO speed where you are taking backup and its an OS utility

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    Gaurav Kumar
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  • 5.  RE: Slow running backup

    Posted Mon June 22, 2020 07:39 AM
    Hi Amit

    Here is a link to an IBM post from 2018 that attempts to address what seems to be the exact issue that you are experiencing...

    https://www.ibm.com/support/pages/slow-ontape-backup-or-archive-informix-database-server-instance

    Bst Rgds

    Kirit

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    Kirit Rana
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  • 6.  RE: Slow running backup

    Posted Mon June 22, 2020 07:59 AM
    Apart from the good insights from Art and Mark, some concurrent activities like update stats, data purging tasks can actually impact Level-0 performance.  Create job schedule that eliminates the concurrent run of such activities.