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  1. #1
    Join Date
    Sep 2002
    Posts
    456

    Arrow Unanswered: Rebalance of tablespaces make database hang

    Hi:

    I am adding new containers to existing tablespaces and during the rebalancing process, database hang for 5 to 10 minutes. During this time I can not do anything e.g. connect, list tablespaces, get snapshot etc. commands. But if I was already connected the database prior to hanging I can do most SQL operations but no db2 or CLP commands.
    Containers are quite large 20G and I am adding two of them to existing two (total of 4 containers at the end).

    Has anybody noticed this behaviour before and any idea why would it hang?

    DB2 UDB V8 FP3 on Windows

    dollar

  2. #2
    Join Date
    Aug 2001
    Location
    UK
    Posts
    4,650

    Re: Rebalance of tablespaces make database hang

    mmm ... I have seen a system hang when rebalance is in progress ... I think it is primarily I/O contention and also other resources used by the rebalancer ...

    The system hang has also happened to me when I was creating a 40 gig tablespace .... I got an error saying that maximum number of processes have been allocated to db2 ... but for sure , it wasn't ... A PMR with IBM did not really help ... The conclusion (!!???) at our shop was that even the resource required to create a connection was not available ....

    (A painful byproduct of this poblem is that the management has strictly said 'No tablespace creation or extension before 10pm )




    Originally posted by dollar489


    Hi:

    I am adding new containers to existing tablespaces and during the rebalancing process, database hang for 5 to 10 minutes. During this time I can not do anything e.g. connect, list tablespaces, get snapshot etc. commands. But if I was already connected the database prior to hanging I can do most SQL operations but no db2 or CLP commands.
    Containers are quite large 20G and I am adding two of them to existing two (total of 4 containers at the end).

    Has anybody noticed this behaviour before and any idea why would it hang?

    DB2 UDB V8 FP3 on Windows

    dollar
    Visit the new-look IDUG Website , register to gain access to the excellent content.

  3. #3
    Join Date
    Sep 2002
    Posts
    456

    Re: Rebalance of tablespaces make database hang

    Well, when the database hang, CPU usage is only around 10% and lot of memory available as well. I think DB2 gets confused somewhere or goes to sleep....can't think of anything at this time. But for DBA's who are considering adding huge containers in future please keep this behaviour in mind.

    dollar

    Originally posted by sathyaram_s
    mmm ... I have seen a system hang when rebalance is in progress ... I think it is primarily I/O contention and also other resources used by the rebalancer ...

    The system hang has also happened to me when I was creating a 40 gig tablespace .... I got an error saying that maximum number of processes have been allocated to db2 ... but for sure , it wasn't ... A PMR with IBM did not really help ... The conclusion (!!???) at our shop was that even the resource required to create a connection was not available ....

    (A painful byproduct of this poblem is that the management has strictly said 'No tablespace creation or extension before 10pm )

  4. #4
    Join Date
    Aug 2001
    Location
    UK
    Posts
    4,650

    Re: Rebalance of tablespaces make database hang

    A question I have :

    How many db2rebal processes can a tablespace use ? Can rebalance exploit SMP parallelism ?

    Thanks for your thoughts

    Sathyaram
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  5. #5
    Join Date
    Sep 2002
    Posts
    456

    Re: Rebalance of tablespaces make database hang

    One thing I found during my investigation was that reblance process will hang if user is trying to execute the snapshot command. DB2 calls it a deadlatch state where both processes are trying to acquire latch of another one. So, DO NOT ISSUE SNAPSHOT command during rebalancing process. I was actually taking the snapshots at various intervals to see the progress!!!

    About the no. of db2rebal processes, I think it's only one (just a guess)

    dollar

    Originally posted by sathyaram_s
    A question I have :

    How many db2rebal processes can a tablespace use ? Can rebalance exploit SMP parallelism ?

    Thanks for your thoughts

    Sathyaram

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