Urgent! Oracle SMON Strangness!!!
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Thread: Urgent! Oracle SMON Strangness!!!

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  1. #1
    Join Date
    Feb 2001
    Posts
    22

    Exclamation

    Hi there,

    We are running Oracle8i Production on 4CPU Sun-Solaris platform.

    Tonight, the Oracle SMON process show strangness. It consumes a lot of CPU resources.

    The PID 1625 is the SMON process.

    Is it possible to reduce the rate of SMON execution ? (As I know, it will be run every 5 minutes)

    Moreover, when the SMON is heavily running, it will increase total SESSIONs too. As a result, the Oracle will run of sessions and work terribly slow.

    We tried to restart Oracle several time, but it did not help.

    load averages: 8.39, 12.43, 14.49 23:50:48
    539 processes: 532 sleeping, 2 running, 5 on cpu
    CPU states: 0.2% idle, 84.8% user, 14.5% kernel, 0.5% iowait, 0.0% swap
    Memory: 4096M real, 63M free, 1993M swap in use, 3210M swap free

    PID USERNAME THR PRI NICE SIZE RES STATE TIME CPU COMMAND
    1625 oracle 1 59 0 308M 284M cpu3 7:03 21.04% oracle
    4626 oracle 1 0 0 2960K 2024K cpu0 0:17 5.61% top
    2772 oracle 1 59 0 309M 289M cpu2 0:11 2.60% oracle
    4509 oracle 1 20 0 313M 293M sleep 0:03 1.90% oracle
    2682 oracle 1 2 0 309M 289M sleep 0:04 1.43% oracle
    4369 oracle 1 52 0 308M 288M sleep 0:04 1.30% oracle
    1808 oracle 1 59 0 313M 293M sleep 0:07 1.11% oracle
    3560 oracle 1 59 0 309M 289M cpu1 0:03 0.98% oracle
    1933 oracle 1 59 0 309M 289M sleep 0:08 0.92% oracle
    4484 oracle 1 59 0 308M 288M sleep 0:02 0.92% oracle
    4467 oracle 1 59 0 309M 289M sleep 0:04 0.87% oracle
    2110 oracle 1 59 0 312M 292M sleep 0:10 0.77% oracle
    1724 oracle 1 59 0 309M 289M sleep 0:07 0.74% oracle
    4643 oracle 1 59 0 308M 288M sleep 0:02 0.73% oracle
    2601 oracle 1 51 0 313M 293M sleep 0:02 0.70% oracle

  2. #2
    Join Date
    Dec 2000
    Posts
    75

    Lightbulb

    You might experience a run-away process or OS problem. Is it possible to reboot?
    goodhealth

  3. #3
    Join Date
    Feb 2001
    Posts
    389
    1) Check for smon timer waits, If u donot see any waits, then your smon is continiously active doing something.
    Check for enteries in v$sort_Segment and also check for TS or ST locks.

    2) If you have uniform extent size for ur tables then u can avoid the free extent coalescing by putting this event in your init.ora file:

    event = "10269 trace name context forever"


  4. #4
    Join Date
    Nov 2000
    Posts
    26

    Thumbs up

    hi,
    SMON does the following primary functions
    1. Instance Recovery at startup
    2. Coalescing space in tablespaces
    3. Cleaning up temporary segments
    i feel that uer problem lies in point no. 3., if uer application has generated a temporary segment very large and that needs to be cleaned after its use then SMON will have to consume excessive resources since the temporary segment has grown very large,
    pls. check up the size of uer temp. segment and confirm , shall advice further
    cheers
    soren

  5. #5
    Join Date
    Jun 2000
    Location
    Madrid, Spain
    Posts
    7,448
    SMON only frees temp extents when you shutdown the database
    If you have no success rebooting Oracle you better try to reboot the server...

  6. #6
    Join Date
    Nov 2000
    Posts
    212
    via v$session and v$sql_area find what smon is executing and how frequently. If a lot of tablespaces where deleted during db life then this can cause slower processing.

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