IDS Forum

RE: RFE request for session details during virtual

Posted By: Alexandre Marini
Date: Tuesday, 2 December 2014, at 10:14 a.m.

In Response To: Re: RFE request for session details during virtual (JACQUES RENAUT)

Thanks a lot, Jacques.
From the manual page, SHMVIRT_ALLOCSEG it says that:

alarm_level: Optional. An integer value
from 1 to 5 that specifies the level of the event alarm to raise:
1 = Not noteworthy, 2 = Information, 3 = Attention (Default), 4 =
Emergency, 5 = Fatal. The event alarm has a class ID of
24 and an event ID of 24003.
Mentioned parameters are both in defaults values, from onconfig:SHMVIRT_ALLOCSEG 0,3
ALRM_ALL_EVENTS 0

What we really need would be the session that demanded an extra ammount of memory to the engine, and caused it to allocate an additional virtual shm segment. That would be perfect for us to identify which session is causing extra memory demands in this box.

We are also trying to lower SHMTOTAL, but that could also not tell us (and most probably won't), which session was
requesting a big amount of mem (when the engine will stop accepting new connections, it will be too late to identify the big memory allocation session).

Thanks anyway, Jacques, if you can find something, please advice.
Regards.

Alexandre Marini
IBM Informix Certified Professional v10 / v11.50 / v11.70 / v12.10

IBM Information Management Informix Technical Professional

IBM Certified Developer - Informix Genero
BRIUG website administrator
Informix independent consultant

> To: ids@iiug.org
> From: jrenaut@us.ibm.com
> Subject: Re: RFE request for session details during virtual [34251]
> Date: Tue, 2 Dec 2014 09:40:38 -0500
>
> Original Post:
>
> I'm not sure if I completely understand the request. But apparently you
> want the SID of the session that caused the new memory segment to be added.
> But this does not necessarily means that that session is the one consuming
> more memory. Specially in an high activity system. Let's assume SID= y is
> doing something nasty and it consumes a lot of memory. At time T0 it
> allocates a large chunk of memory for a sort or whatever. Between T0 and T1
> a lot of other sessions allocate small ammounts of blocks. At T1 a
> different session (SID=y) needs some memory that isn't available, and that
> triggers a new segment allocation. You'd get SID=y and not SID=x in the
> messge.
>
> Beside that, systems can now allocate memory in pro-active mode (meaning no
> SID is associated with it).
>
> What I think you need is an expedite way of showing which sessions are
> consuming more memory at a specific time (onstat -u is limmited for that,
> and I do agree some other option would be interesting). Once you have a way
> to do that (and we can create a script to do what you mention) you just
> have to call it in the ALARMPROGRAM script when the event is the one you're
> looking for...
>
> Regards
>
> On Mon, Dec 1, 2014 at 5:32 PM, Alexandre Marini <alexandre@briug.org>
> wrote:
>
> > Hello.
> > I think this might be a very useful RFE, in order to help us to identify
> > abnormal memory session usage, in OLTP systems of high ammount of
> > concurrent
> > sessions (ad-hoc applications).
> >
> > If anyone like, please vote it...
> > https://www.ibm.com/developerworks/rfe/execute?use_case=viewRfe&CR_ID=62730
> >
> > Regards.
> >
> > Alexandre Marini
> > IBM Informix Certified Professional v10 / v11.50 / v11.70 / v12.10
> >
> > IBM Information Management Informix Technical Professional
> >
> > IBM Certified Developer - Informix Genero
> > BRIUG website administrator
> > Informix independent consultant
> >
> >
> >
> >
> *******************************************************************************
> > Forum Note: Use "Reply" to post a response in the discussion forum.
> >
> >
>
> Reply:
>
> If I'm reading code correctly, it looks like if you have ALRM_ALL_EVENTS set
> to 1 in your $ONCONFIG then adding a segment would generate an alarm. I missed
> noticing the alarm number/type/severity etc...but it did look like it called
> invoke_alarm() so something would be generated which could do something
> specific in the alarm program. Otherwise, it's not too hard to write a script
> which detects when segments are added and then could kick off onstats. I think
> I might have one of these already, I'll see if I can't find it.
>
> Jacques Renaut
> IBM Informix Advanced Support
> APD Team
>
>
> *******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>

Messages In This Thread

• RFE request for session details during virtual shm
  Alexandre Marini -- Monday, 1 December 2014, at 12:32 p.m.
  • Re: RFE request for session details during virtual
    Fernando Nunes -- Monday, 1 December 2014, at 1:40 p.m.
    • Re: RFE request for session details during vir....
      Art Kagel -- Monday, 1 December 2014, at 2:53 p.m.
      • Re: RFE request for session details during vir....
        Fernando Nunes -- Monday, 1 December 2014, at 5:05 p.m.
        • RE: RFE request for session details during vir....
          Alexandre Marini -- Tuesday, 2 December 2014, at 5:53 a.m.
    • Re: RFE request for session details during virtual
      JACQUES RENAUT -- Tuesday, 2 December 2014, at 9:40 a.m.
      • RE: RFE request for session details during virtual
        Alexandre Marini -- Tuesday, 2 December 2014, at 10:14 a.m.
    • RE: RFE request for session details during vir....
      Paul Watson -- Tuesday, 2 December 2014, at 9:49 a.m.
      • RE: RFE request for session details during vir....
        Alexandre Marini -- Tuesday, 2 December 2014, at 10:26 a.m.
        • RE: RFE request for session details during vir....
          Paul Watson -- Tuesday, 2 December 2014, at 10:32 a.m.
          • RE: RFE request for session details during vir....
            Alexandre Marini -- Tuesday, 2 December 2014, at 11:04 a.m.

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