The whole thing comes as a consequence of using buffered I/O. New linux kernels (2.4.18 and later) have new memory management, which allows
the kernel to grab more memory for buffers in periods of intense I./O activity. If you have a very active database on ReiserFS or Ext3, Linux is
going to try to help you out by allocating more memory for the file system buffers, even by stealing pages from the active processes, which will, in turn. start paging. The only possible response is to eliminate the buffered I/ O and switch to non-buffered I/O. That is not so hard to do.


On 2003.11.01 09:44, Tanel Poder wrote:
Just for clarification, do you actually see swapping when starting a new
process or you just guess linux would swap because you don't see "free"
memory in top output?

Tanel.

  ----- Original Message -----
  From: Sai Selvaganesan
  To: Multiple recipients of list ORACLE-L
  Sent: Saturday, November 01, 2003 1:34 AM
  Subject: RE: memory usage by dbw very high


rich
the ipcs output shows 1.1 gb. so nearly 2 gb(total ram size is 3.08) is
used by non shared memory size.
i went thru all the processes and found dbwr using the max %mem. what could
be the reason?
sai


  "Jesse, Rich" <[EMAIL PROTECTED]> wrote:
    If I'm not mistaken, this figure includes the size of the shared memory
    segment from the SGA. Take the output of the "oracle" line of "ipcs -a"
    (hopefully you'll only have one!) and subtract it from the process size
to
    get a better idea of the non-shared memory size of the process.

Rich

    Rich Jesse System/Database Administrator
    [EMAIL PROTECTED] Quad/Tech Inc, Sussex, WI USA


-----Original Message----- Sent: Friday, October 31, 2003 3:49 PM To: Multiple recipients of list ORACLE-L


hi


    i have a system that has no active users at this point of time. the
memory
    used by the dbw process is very high leading to a lot of swapping when
any
    process starts.
    here are the spces
    version:9.2.0.4
    os:Linux 2.4.9-e.24smp
    o/p from top:
    1:44pm up 29 days, 23:55, 4 users, load average: 1.73, 1.68, 1.35
    132 proces! ses: 131 sleeping, 1 running, 0 zombie, 0 stopped
    CPU0 states: 24.4% user, 2.2% system, 0.0% nice, 72.2% idle
    CPU1 states: 0.5% user, 0.5% system, 0.0% nice, 98.0% idle
    CPU2 states: 0.0% user, 0.1% system, 0.0% nice, 99.4% idle
    CPU3 states: 0.3% user, 0.4% system, 0.0% nice, 98.3% idle
    Mem: 3089964K av, 3083380K used, 6584K free, 846848K shrd, 193448K
    buff
    Swap: 2048152K av, 1652K used, 2046500K free 1852468K
    cached
    sga size:
    Total System Global Area 1084823632 bytes
    Fixed Size 452688 bytes
    Variable Size 335544320 bytes
    Database Buffers 738197504 bytes
    Redo Buffers 10629120 bytes
    pga aggregate size:700M
    and ps o/p of dbw process
    USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
    oracle 4062 0.0 16.4 1131260 508168 ? S 10:16 0:06
    ora_dbw0_revenue

please advise. what is really going on.

    thanks
    sai
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    Please see the official ORACLE-L FAQ: http://www.orafaq.net
    --
    Author: Jesse, Rich
    INET: [EMAIL PROTECTED]

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