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  1. #1
    Join Date
    Dec 2016
    Posts
    2

    Unanswered: IO performance issues

    Hi,
    I want to begin by saying I'm relatively new with Informix and don't have advanced knowledge of how informix works.

    I'm opening this thread because of some IO performance issues that I have now and need to be sure of what I must do.

    This is my db profile counts:Profile
    dskreads pagreads bufreads %cached dskwrits pagwrits bufwrits %cached
    22906487 87848814 34363980245 99.93 332057743 398328761 1082072410 69.31

    isamtot open start read write rewrite delete commit rollbk
    48406998458 7423608018 9188986012 10875359326 1488886 347373130 682316 347179506 1

    gp_read gp_write gp_rewrt gp_del gp_alloc gp_free gp_curs
    1487097310 353965214 343076548 4397605 4723657 2 18018239

    ovlock ovuserthread ovbuff usercpu syscpu numckpts flushes
    0 0 0 457810.60 98673.63 3364 7580

    bufwaits lokwaits lockreqs deadlks dltouts ckpwaits compress seqscans
    541933 6627626 13923560081 0 0 29422 1170160 807177

    ixda-RA idx-RA da-RA logrec-RA RA-pgsused lchwaits
    70449 9643446 760355 1294 18020622 137838512

    Onconfig:
    NETTYPE soctcp,1,200,NET
    LISTEN_TIMEOUT 60
    MAX_INCOMPLETE_CONNECTIONS 1024
    FASTPOLL 1
    NUMFDSERVERS 4
    NS_CACHE host=900,service=900,user=900,group=900

    MULTIPROCESSOR 1
    VPCLASS cpu,num=12,noage
    VP_MEMORY_CACHE_KB 0
    SINGLE_CPU_VP 0
    CLEANERS 8
    DIRECT_IO 1
    LOCKS 20000
    DEF_TABLE_LOCKMODE page
    RESIDENT 0
    SHMBASE 0x44000000L
    SHMVIRTSIZE 10485760
    SHMADD 262144
    EXTSHMADD 51200
    SHMTOTAL 62914560
    SHMVIRT_ALLOCSEG 0,3
    SHMNOACCESS
    MAX_PDQPRIORITY 100
    DS_MAX_QUERIES
    DS_TOTAL_MEMORY
    DS_MAX_SCANS 1048576
    DS_NONPDQ_QUERY_MEM 256
    DATASKIP
    BUFFERPOOL default,buffers=10000,lrus=8,lru_min_dirty=50,lru_ max_dirty=60.5
    BUFFERPOOL size=2K
    BUFFERPOOL size=8K

    The machine on which DB runs has 16 cpus and 64 GB of RAM.

    These values are not configured by me.

    Any ideeas ?

    Thanks.

  2. #2
    Join Date
    Dec 2016
    Posts
    2
    onstat -P
    Percentages:
    Data 55.67
    Btree 8.09
    Other 36.24

    onstat -F

    Fg Writes LRU Writes Chunk Writes
    2 611239 14997845

    address flusher state data # LRU Chunk Wakeups Idle Tim
    4c3e48e8 0 I 0 603 10296 1021956 1010204.637
    4c3e51a8 1 I 0 707 9448 1021391 1009724.104
    4c3e5a68 2 I 0 627 7475 1019552 1010959.875
    4c3e6328 3 I 0 873 4565 1017161 1011482.790
    4c3e6be8 4 I 0 742 7209 1019094 1010744.211
    4c3e74a8 5 I 0 727 6145 1018085 1010709.286
    4c3e7d68 6 I 0 858 7217 1019100 1010542.952
    4c3e8628 7 I 0 773 6640 1018665 1010826.101
    states: Exit Idle Chunk Lru

    onstat -g mgm

    IBM Informix Dynamic Server Version 12.10.FC6 -- On-Line -- Up 11 days 18:00:30 -- 10595476 Kbytes

    Memory Grant Manager (MGM)
    --------------------------

    MAX_PDQPRIORITY: 100
    DS_MAX_QUERIES: 6144
    DS_MAX_SCANS: 1048576
    DS_NONPDQ_QUERY_MEM: 256 KB
    DS_TOTAL_MEMORY: 62856488 KB

    Queries: Active Ready Maximum
    0 0 6144

    Memory: Total Free Quantum
    (KB) 62856488 62856488 10224

    Scans: Total Free Quantum
    1048576 1048576 1

    Load Control: (Memory) (Scans) (Priority) (Max Queries) (Reinit)
    Gate 1 Gate 2 Gate 3 Gate 4 Gate 5
    (Queue Length) 0 0 0 0 0

    Active Queries: None

    Ready Queries: None

    Free Resource Average # Minimum #
    -------------- --------------- ---------
    Memory 0.0 +- 0.0 7857061
    Scans 0.0 +- 0.0 1048576

    Queries Average # Maximum # Total #
    -------------- --------------- --------- -------
    Active 0.0 +- 0.0 0 0
    Ready 0.0 +- 0.0 0 0

    Resource/Lock Cycle Prevention count: 0
    Last edited by steven`; 12-08-16 at 07:14.

  3. #3
    Join Date
    May 2008
    Posts
    36
    Hi,

    the problem is, posting a few onstats doesn't help very much because the server may have been running over al long time, so these value may be taken out of context.
    You have to be more specific on the performance issue you are facing (when / how long / what exactly is slow / what was changed ? and so on ). If you are sure it is an IO problem you have to fix the hardware first.
    What I can see i (may be out of context)


    2 FG Writes : Meaning a thread needed to flush buffers to disk which can be very IO intensive.

    Furthermore, this seems strange:

    BUFFERPOOL default,buffers=10000,lrus=8,lru_min_dirty=50,lru_ max_dirty=60.5
    BUFFERPOOL size=2K
    BUFFERPOOL size=8K

    The second line and third line should default to:
    BUFFERPOOL size=2K,buffers=1000,lrus=8,lru_min_dirty=50,lru_ max_dirty=60
    BUFFERPOOL size=8K,buffers=1000,lrus=8,lru_min_dirty=50,lru_ max_dirty=60

    which is WAY to small for a productive system (2000K / 8000 K respectively) The third line only makes sense if you are using 8K Dbspaces (see onstat -d).
    If no other applications are runnig on the system, you can set the total size of them to be equal to 25 or 50 % of 64 GB, but it depends on your system.
    As for the MGM, yo have to be more specific on why you want o use it.

  4. #4
    Join Date
    Sep 2011
    Location
    Pont l'Abbé, Brittany, France
    Posts
    394
    Provided Answers: 1
    Hi,

    as wowbagger says, your buffer pool seems t be way too small, this is what onstat -F says. You have lots of memory, so why not mutliply the BUFFERPOOL ( 2k), by 2.
    Your write cache is very bad, this should help
    Eric

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