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  1. #1
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    Jan 2003
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    Unanswered: DB2 goes mad using CPU for no particular reason

    Hi,
    in January current year we have migrated to DB2 Enterprise Edition v9.5 fixpack 2 on Linux and DB2 was working without any problem at all. Only two times so far on weekends (Saturday or Sunday) there was some extensive CPU usage on DB2. Process db2sysc was going mad and consumed 100% of CPU for hours despite usually on weekends there is no more then 10% CPU peek. I have analyzed db2diag.log file and there was absolutely no error or any other message for hours in this file. It looks like DB2 stopped logging to db2diag.log and the only message is then DB2 manager is starting up. There was also no application connected to database at the time that would consume CPU. After about 1 hour of extensive CPU usage applications couldn't connect on database any more. So there was a night wake-up call. I have checked and db2sysc process was constantly consuming more and more CPU power with no particular reason, there was no application connected on database that would consume CPU!

    This kind of behaviour is extremely strange. On weekends there is almost no application activity on DB2. On week-day there are 100-times more DB2 transactions then on weekends.

    On migration day on this database I have turned on self-tuning for every parameter that was possible to turn on and DB2 was working like a charm (way better performance). I just have an assumption that DB2 recognizes that there is very little activities on database and self-tuning is executing some tasks that goes mad. Just an assumption... I don't know what is happening because there are no info in log files.

    Anyone experiencing the same problem? Any idea what should I check?
    Regards
    Last edited by grofaty; 09-09-09 at 07:42.

  2. #2
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    Jan 2003
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    Provided Answers: 5
    We had a similar problem a few months ago, but it would happen randomly throughout the day. DB2 would just seem to hang from just a minute or so to nearly an hour. We opened a PMR with IBM and found that DB2 was doing some memory defragmentation in one of the caches. When it decided to do this, the system would hang until it finished. The solution was to set db_mem_thresh to 100.

    You can try this, but I would suggest that you open a PMR with IBM. They have some better diagnostic tools with v9.5, especially when the systems seems to hang.

    Andy

  3. #3
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    Jan 2003
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    ARWinner,
    your description looks like my second problem!!! It just looks like that DB2 freezes for some seconds: 5 to 20 seconds reported by end-users. They just reported that running the same application 10-times runs in fraction of second, but some times it runs for 10 seconds. This started to happend 14-days ago according to end-user report.
    In my case DB_MEM_THRESH is set to default value of 10. Any more info is greatly appreciated.
    Thanks a lot.

  4. #4
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    Jun 2003
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    Provided Answers: 1
    You could use the db2top tool for additional troubleshooting.
    ---
    "It does not work" is not a valid problem statement.

  5. #5
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    If you are getting hangs, then I would open a PMR and get it fixed.

    Andy

  6. #6
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    Quote Originally Posted by n_i
    You could use the db2top tool for additional troubleshooting.
    I have executed db2top command with db2inst1 super-user and got error:
    "-bash: db2top: command not found"

    According to documentation:
    "db2top is a monitor for DB2 UDB specifically designed for
    DPF environments. It provides a unified, ’single system
    view’ of a multi-partition DB2 database."

    We are not using DPF, so this tool is not available in our ESE version.

  7. #7
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    Provided Answers: 1
    It should be included with 9.5. fp2. I'm not sure if it is installed in ~/sqllib/bin, which is in the path. Try searching for it, e.g.
    Code:
    find ~/sqllib -name db2top -ls
    ---
    "It does not work" is not a valid problem statement.

  8. #8
    Join Date
    Jan 2003
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    Hi,
    I have tried to search the whole disk:
    Code:
    sudo find / -name db2top -ls
    but no program was found.

    Is this program installed separately? Is this Linux/Intel specific? This my DB2 is on Linux on hardware: System_z.
    Regards
    Last edited by grofaty; 09-10-09 at 08:54.

  9. #9
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    Provided Answers: 5
    db2top should be in {INSTHOME}/sqllib/bin/. That is where it is in our environment, which is RH linux single partition DB2 is ESE. We are using V9.5 FP 4 and FP 3a.

    Andy

  10. #10
    Join Date
    Jan 2003
    Posts
    1,605
    Hi,
    I have checked on Suse Linux on "System z" DB2 ESE single partition v9.5 FP 2. But db2top is not available in any path.

    But I have checked on other test Intel computer: DB2 v9.7! and db2top is in /opt/ibm/db2/V9.7/bin/db2top. But I don't have any db2 v9.5/intel, to check if this is Linux/Intel specific.
    Regards

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