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I am installing Oracle 10.2.0.4.0 on a linux server running RH 5.x with 18gb of memory. According to the Oracle install guide it recommends a swap space equal to total memory or 18gb. Does it really require swap space of 18gb? If I allocate less space for swap (say 8gb), will that have any adverse effects?

Thanks in advance,
Bill--
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  • Lyallbarbour_at_sanfranmail.com at Mar 25, 2010 at 5:30 pm
    I can't give any technical references, but i can say what i did. When the installer complained about wanting 18gb of swap for our HP-UX Itanium Oracel 11.1.0.6 install, i tried to bypass it with only 4gb. It worked fine. The SA said he couldn't get to expanding it right away, and i got impatient.
    Just my experience.

    -----Original Message-----
    From: Bill Zakrzewski
    To: Oracle-L_at_freelists.org
    Sent: Thu, Mar 25, 2010 1:25 pm
    Subject: Swap Space

    I am installing Oracle 10.2.0.4.0 on a linux server running RH 5.x with 18gb of
    emory. According to the Oracle install guide it recommends a swap space equal
    o total memory or 18gb. Does it really require swap space of 18gb? If I
    llocate less space for swap (say 8gb), will that have any adverse effects?
    Thanks in advance,
    ill--
    ttp://www.freelists.org/webpage/oracle-l

    --
    http://www.freelists.org/webpage/oracle-l
  • Andrew Kerber at Mar 26, 2010 at 2:32 am
    The swap space is a problem if the system is using eager swap, that is if
    the OS marks swap as allocated when the RAM as allocated. When the system
    uses eager swap, and the swap space isnt set per the recommendation, and if
    your database uses a significant amount of memory, you are likely to run
    into problems that look like problems with insufficient memory, even when
    it is actually a problem with insufficient swap.
    On Thu, Mar 25, 2010 at 9:13 PM, De DBA wrote:

    In my experience this should read: "... will likely crash the database.".
    The Linux kernel includes a process called "oom-killer", which in an
    Out-Of-Memory (OOM) situation will try to identify and forcefully kill idle
    memory hogs using some advanced algorithms.

    Unfortunately with Oracle processes, the most important such as SMON in the
    database and OPMN in the oracle app server may seem perfect candidates for
    this as they tend to be idle most of the time and allocate a lot of memory.
    Killing these of course is not a good idea, but it does free up memory. It
    may also kill other vital but usually near-idle processes, causing the OS to
    become unresponsive.

    The oom-killer logs its actions to syslogd, so you can always find a trail
    showing why the database crashed (assuming that /var is not full and you do
    log kernel messages).

    I am not sure that kswapd pushes up the average load by itself, as this
    reflects the average number of runnable processes, but I am not a kernel
    expert by any measure so I may well be wrong here. Incidentally, a load of
    40 doesn't strike me as awfully high on 8 (16?) cores. It works out to
    2.5-5/core. I've seen dual core machines work quite happily, if not
    extremely slowly, with loads up to 10-15 per core. At any rate, the number
    of runnable processes is not a reliable measure for memory usage.

    Cheers,
    Tony

    On 26/03/10 6:26 AM, Martin Bach wrote:

    Hi Bill,

    just my 0.02 worth. The amount of swap the installer requires is a bit mad
    with lots of memory like Howard already pointed out. The amount of swap
    you need depends on your application, bear in mind that if the system runs
    out of memory and swap it will crash. Before that it will become quite
    unusable since the kswapd daemon(s) will agressively try to free memory.
    This process can and will push the load average very high, and if no
    substantial amount of memory can be freed causing kswapd to sleep again
    your system is likely to become completely unresponsive to the point where
    it will have to be rebooted. Just happened to me today-the last stats top
    reported was a load average of 40 with a 8 dual core opteron box, but I
    expect it went much higher than that.

    So if your application is gentle on memory then you only need a little
    amount of swap (just for that warm fuzzy feeling), but if you know that
    the box is going to be hit hard you might want to add some extra swap
    space for peace of mind. Once you did that, tune the application to use
    less memory-there are plenty of articles out there helping you with that
    task.

    Hope that helps,

    Martin

    No the estimates by the installer get a bit mad with a large amount of
    memory
    On 25/03/2010, Bill Zakrzewski wrote:

    I am installing Oracle 10.2.0.4.0 on a linux server running RH 5.x with
    ...
    Thanks in advance,
    Martin Bach
    OCM 10g
    http://martincarstenbach.wordpress.com

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    --
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    --
    Andrew W. Kerber

    'If at first you dont succeed, dont take up skydiving.'

    --
    http://www.freelists.org/webpage/oracle-l

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