IDS Forum

Re: IDS 12.10 on HP-UX- DS Total Memory

Posted By: Martin Fuerderer
Date: Friday, 22 July 2016, at 9:25 a.m.

In Response To: Re: IDS 12.10 on HP-UX- DS Total Memory (MOHD FADZIL JUSOH)

Hi,

right, for HP-UX on Itanium the "Machine Specific Notes" (aka "Machine=20
Notes")
tell that the Informix configuration parameter SHMBASE should be set to=20
0x0L .

Whether the Informix server is running in a virtual machine or on 'bare=20
metal' does
not matter - the setting of SHMBASE depends on the operating system that=20
is used.

[ What it specifies is the location where the shared memory that=20
Informix allocates

gets mapped to within the memory address space of the "oninit"=20
processes.

Occupants of this address space are the text and data segments=20
(basically where

the binary code of the executable gets loaded), the stack, the heap,=20
shared libraries,

etc. ... and shared memory segments. Where these things are located=20
(i.e. mapped

to) and in which direction they can grow when needed, depends on the=20
operating

system.

For the shared memory segments of the Informix server, the aim is to=20
have them as

contiguous as possible. I.e. even when several segments get allocated=20
over time, their

use can be more efficient when they are adjacent in the memory space=20
rather then

dispersed (which results in more fragmentation of the memory space).

With a value of 0x0L on HP-UX, I think the OS is intelligent enough to =

figure out the best

place by itself. (I'm quite sure that SHM segments of Informix do not=20
really start at address

0x0 ... one could check by looking at something equivalent to=20
/proc/<pid>/maps .) ]

For the Informix server there are no specific parameters for running in a=20
virtual machine
environment - as already mentioned by Art Kagel, et al. After all, this=20
would be against
the basic idea of a virtual machine, which is that an application like=20
Informix does not need
to know about the fact that it is running in a virtual machine.

However ... there are some things to know:

- a virtual machine may pretend that there is more memory than physically=20
exists. The
virtual machine manager most probably will use a technique like=20
swapping, paging, etc.
to cover any bottlenecks. If this happens, it will most probably be=20
noticed as a (grave)
peformance problem for the Informix server.

- a virtual machine manager may distribute the existing CPU resources=20
among several virtual
machines ... on a time slice basis or similar. In such a case, it=20
probably does not make much
sense to configure the Informix server with processor affinity ... as=20
the virtual machine
manager may switch the CPUs given to the virtual machine - without even=20
letting the OS in the
virtual machine know about this.

The best case for Informix server in a virtual machine is when hardware=20
rescources, especially
CPUs and memory, are directly and exclusively dedicated to the virtual=20
machine. This is the only
way to get somewhat predictable performance results in a virtual machine=20
environment.
Everything else leaves you always with a big "it depends" ... no matter=20
what the people in
charge of the virtual machine manager might tell you. :-)

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

Read about the Informix Warehouse Accelerator:
http://tinyurl.com/the-iwa-blog

IBM Deutschland Research & Development GmbH
Chairman of the Supervisory Board: Martina Koederitz
Board of Management: Dirk Wittkopp
Corporate Seat: Boeblingen, Germany
Reg.-Gericht: Amtsgericht Stuttgart, HRB 243294

From: "MOHD FADZIL JUSOH" <fadzil@isianpadu.com>
To: ids@iiug.org
Date: 07/22/2016 04:21
Subject: Re: IDS 12.10 on HP-UX- DS Total Memory [37470]
Sent by: ids-bounces@iiug.org

Hi,=20

Value for SHMBASE based on machine noted, I just need follow this value=20
right?=20

#SHMBASE 0x0L=20

Our new enviroment IDS 12.10 will run on Virtual Machine. Any different=20
configration we need to tune on onconfig parameter for virtual machine?=20

Thank You=20

***************************************************************************=
****=20

Forum Note: Use "Reply" to post a response in the discussion forum.=20

Messages In This Thread

• IDS 12.10 on HP-UX- DS Total Memory
  MOHD FADZIL JUSOH -- Thursday, 21 July 2016, at 11:01 a.m.
  • RE: IDS 12.10 on HP-UX- DS Total Memory
    Mike Walker -- Thursday, 21 July 2016, at 11:14 a.m.
  • Re: IDS 12.10 on HP-UX- DS Total Memory
    Art Kagel -- Thursday, 21 July 2016, at 2:21 p.m.
    • Re: IDS 12.10 on HP-UX- DS Total Memory
      MOHD FADZIL JUSOH -- Thursday, 21 July 2016, at 10:01 p.m.
      • Re: IDS 12.10 on HP-UX- DS Total Memory
        Art Kagel -- Thursday, 21 July 2016, at 10:11 p.m.
        • Re: IDS 12.10 on HP-UX- DS Total Memory
          MOHD FADZIL JUSOH -- Thursday, 21 July 2016, at 10:20 p.m.
          • Re: IDS 12.10 on HP-UX- DS Total Memory
            Art Kagel -- Friday, 22 July 2016, at 12:14 a.m.
          • Re: IDS 12.10 on HP-UX- DS Total Memory
            Martin Fuerderer -- Friday, 22 July 2016, at 9:25 a.m.

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