IDS Forum

Re: onmode -r on AIX?

Posted By: Martin Fuerderer
Date: Tuesday, 15 May 2007, at 11:01 a.m.

In Response To: Re: onmode -r on AIX? (Maeve Devine)

Hi,

it should use the SHMBASE that you have set in your onconfig
file. If you have doubts about that, please check that your environment
is set correctly, especially $INFORMIXDIR and $ONCONFIG.

Actually I rather think you are really hitting the limit. But you can
check
how much SHM has been allocated. See for the number of messages
in the online.log message file that say like "... SHM ... allocated ..."
and
add up the size numbers. This should give you an estimate how much
memory was allocated and whether it really hits the limit or there is
another problem.

As far as I know on AIX in a 32-bit runtime environment (which is what
you use with a 32-bit IDS version), there are several limits and
default settings at work:

- SHM segments by default are 256 MB. Therefore try to have
onconfig settings so that SHM segments will be allocated in
256 MB pieces. Other settings will waste memory.
This default SHM segment size can be changed somehow (on
OS level), but currently I can't tell the details. :-(

- The number of SHM segments is limited to 11 (for application
allocated SHM). An additional 5 segments are reserved for
special purposes (kernel, text, libraries, etc.).
Therefore try to avoid using SHM connection protocol (onipcshm),
as these SHM segments will be fairly small and thus waste memory.
Instead use TCP connection protocol only.

- The total limit of SHM that can be allocated is about 2.75 GB.
This is due to the addressable memory space of a 32-bit application.

You can use system utility "vmon [-l] -P <pid>" to monitor memory
usage of a process. The output is a bit cryptic, though.

If you have an optional package installed, called "Performance Tools",
then you can use "/proc/map" pseudo files similar to Linux or Solaris
to look at a processes memory map. This may be easier to read.

[ Minimum and maximum SHM segment sizes:

If the minimum size is too big (compared to IDS configuration), then you
would waste memory and possibly hit the out-of-memory limit earlier
than expected. I'm not sure if "ipcs -m" as user root would show the
requested size only, or the entire size of such SHM segments.

If the maximum size is configured too small (compared to IDS
configuration), then IDS will get only small segments and simply
require more of them (expecting them to be contiguous) to satisfy the
needs. This surely can be seen by using "ipcs -m" as user root.
In this case it is possible to hit the maximum number of SHM
segments earlier than expected.
]

If all this is too compilated and the limit of 2.75 GB is too low anyway,
then I would recommend the 64-bit version of IDS. This will have much
less restrictions in this regard. Possibly you then should consider
using AIX 5.3 (rather than 5.1).

Regards,
Martin
--
Martin Fuerderer
IBM Informix Development Munich, Germany
Information Management

IBM Deutschland GmbH
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Board of Management: Martin Jetter (Chairman), Rudolf Bauer, Christian
Diedrich, Christoph Grandpierre, Matthias Hartmann, Thomas Fell, Michael
Diemer
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ids-bounces@iiug.org wrote on 15.05.2007 15:26:02:

> I don't believe you can set SHMMAX and SHMSEG on AIX, it's supposed to
> self-tune. I do know it's limited to 11 or 12 segments per process. To
get
> around this I normally just set a high SHMVIRTSIZE so it doesn't need to
be
> creating loads of segments. The final error it is giving is the same as
what
> happens when during normal usage it hits this limit.
>
> But this isn't normal usage. A brand new instance with nothing in it. I
have
> nothing else running on the box. I rarely touch ontape and have this
feeling
> there is a parameter or command I'm missing. It is trying to use the
wrong
> SHMBASE - 14:27:47 Contiguous shared memory segment allocation failed at

> 0xd0000000.
> Allocation retried at 0xe0000000.
>
> Why won't it use the SHMBASE I've set in the onconfig??
>
> Thanks,
> Maeve
>
> "ART KAGEL, BLOOMBERG/ 731 LEXIN" <kagel@bloomberg.net> wrote: Did you
check
> that the Kernel parameter SHMSEG and SHMMAX are large enough to
> accomodate IDS's shared memory requirements - as suggested in the log
message?
>
> Art S. Kagel
>
> ----- Original Message -----
> From: Maeve Devine
> At: 5/15 5:37:35
>
> Hi All,
>
> IDS 9.40.UC4 on AIX 5.1. I have reports of the same behaviour with IDS
10 but
> I havn't tested that myself.
>
> I cannot get a cold restore + logical logs working on AIX. It works on
> Solaris.
>
> It is when I choose to restore the logical logs that it fails. Works if
I
> don't restore the logs.
>
> To the online.log it reports:
>
> 14:27:47 Dynamically allocated new virtual shared memory segment (size
8192KB)
> 14:27:47 Contiguous shared memory segment allocation failed at
0xd0000000.
> Allocation retried at 0xe0000000.
> Check SHMBASE is consistent with the value in
$INFORMIXDIR/etc/onconfig.std.
> Consider using a different SHMBASE value in your ONCONFIG file.
> If shared memory segments are not allocated in increasing address order,

> memory block allocation performance may degrade.
>
> 14:27:47 Dynamically allocated new virtual shared memory segment (size
8192KB)
> 14:27:47 shmat: [EMFILE][24]: out of shared memory segments, check
system
> SHMSEG
>
> 14:27:47 out of virtual shared memory
>
> 14:27:47 Assert Warning: ISAM error: An error has occurred during
logical
> restore.
>
> My SHMBASE in onconfig and onconfig.std are the same and different to
the one
> reported above, namely 0x30000000L. The above value is incorrect. I
tried
> making my SHMVIRTSIZE much higher so it doesn't need to add new segments
but
> it tried anyway. I adjusted the SHMADD size and that was reflected in
the
> error message, so it is reading my onconfig.
>
> My steps are:
>
> 1. level 0 archive: ontape -s
> 2. Back up logical logs: ontape -a
> 3. Server offline
> 4. Restore level 0 archive and when prompted my logs: ontape -r
>
> Both logs and archive are written to files on disk rather than a tape
device.
>
> Attached the full log (test.log), the af file and the onconfig (test).
I'm
> flummoxed, would appreciate any tips.
>
> Thanks,
> Maeve
>
> ---------------------------------
> Don't get soaked. Take a quick peak at the forecast
> with theYahoo! Search weather shortcut.
>
>
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>

Messages In This Thread

• onmode -r on AIX?
  Maeve Devine -- Tuesday, 15 May 2007, at 5:37 a.m.
  • Re: onmode -r on AIX?
    ART KAGEL, BLOOMBERG/ 731 LEXIN -- Tuesday, 15 May 2007, at 8:59 a.m.
    • Re: onmode -r on AIX?
      Maeve Devine -- Tuesday, 15 May 2007, at 9:26 a.m.
      • RE: onmode -r on AIX?
        Priest, Darryl -- Tuesday, 15 May 2007, at 10:24 a.m.
      • Re: onmode -r on AIX?
        Martin Fuerderer -- Tuesday, 15 May 2007, at 11:01 a.m.
        • Re: onmode -r on AIX?
          Maeve Devine -- Tuesday, 15 May 2007, at 11:44 a.m.

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