Re: What means: Shared memory realm does not exist?

From: Some One Else <algernon_at_spamcop.net>
Date: Sun, 16 Sep 2001 05:12:03 GMT
Message-ID: <DwWo7.5196$RS3.3231774@news1.elcjn1.sdca.home.com>

Hello,

I've looked all over the net and through the various Oracle and Linux documentation, but can't find anywhere that discusses in detail what kernel parameters are available for tweaking shared memory and how to do it. Based on a page designed for 9i, here's what I've put in my rc.local file:

  echo 250 32000 100 128 > /proc/sys/kernel/sem   echo 256000000 > /proc/sys/kernel/shmmax

This doesn't do the trick. I don't think Oracle is starting up at all based on what I'm seeing from "ps -A | grep ora" .

On win95, using sqlplus was enough to start the database. This was also true the first time I started the database when it worked. I've also tried the 'dbstart' command, but it does nothing -- no messages or anything, and no 'ps -A' activity afterwards.

I notice in your example that you use a 'bc' command as part of the piping. What does this do for you? Trying 'man bc' gets me no info.

Thanks for any help!

johnt_at_tman.dnsalias.com wrote:

> Howard J. Rogers <howardjr_at_www.com> wrote:

>> The absolute bog-standard typical cause as far as my (limited) Linux
>> experience suggests is that your kernel parameters (sem and shmmax,
>> usually) were not set to sufficiently high values; or (speaking from
>> bitter experience) even when you remember to set them to the right
>> values, you forget to re-boot the Linux box to allow them to take effect.

>
> Actually, I have seen omission of tuning shmmax and sem to result in an
> error in the alert file, something to the effect of "unable to create
> shared mem
> segment of size....". Oracle still starts, but will not be able to use
> all of its buffer cache.
>
> The tricky thing is that when you set these to the right values via the
> /proc/sys/... interface, they take effect immediately.... but are reset
> when you reboot the box :(. You must script somewhere to update them
> when the box reboots.
>
> I have 512MB max SGA. This is a line that I put in the local boot file...
>
> echo "512 * 1024^2" | bc > /proc/sys/kernel/shmmax
>
> (kernel 2.4.x)
>
> JT.
>
>

>>> Received on Sun Sep 16 2001 - 00:12:03 CDT