RE: AIX and Informix
Chafik, Basim
a raw device for Informix. The reason is the first block is used to host
information or meta data about the logical volume including the LVID. This
information is also hosted in the ODM which is a kind on internal database
that AIX uses to keep information about all it devices (it is also the
reason why AIX can do many operation online like increase decrease File
system size and adding disks and volumes online..etc). In normal operation
AIX will not refer back to the disk or LV to get its meta data because AIX
already has in the ODM. But with certain maintenance operation and low level
command, they query those area directly and if it was over written then the
operation will fail. For example the import of the volume group importvg,
syncvg synclvodm..and many more commands. I am not 100% sure if IBM
internally protected this information and actually start after that LVDA
(logical volume descriptor area) block, but in the older AIX versions that
was the practice to leave an offset and it was carried forward since then
(at least for me).
I have experience in all flavors of Unix and I have to say the AIX is my
favorite. From my experience with clients it is the most stable and has the
highest availability (I have a client on AIX 4.3.3 with almost 1000 days of
uptime, Obviously they did not have to install any patch during this
period!!?). Non of the other Unix flavors can do maintenance (like kernel
tuning) dynamically and online. AIX does in most cases. HACMP on the other
hand, I had bad experience with. This was in the old days of AIX 4x, But
since then the bad experience memories stuck with it and did not change till
now even that IBM might improved it a lot.
Basim Chafik
Senior Systems Analyst
IBM Certified Advanced Technical Expert (CATE)
1.800.688.4895
basim....@plx.com
plexus (Division of BancTec)
-----Original Message-----
From: tom...@yahoo.com [mailto:tom...@yahoo.com]
Sent: Friday, October 20, 2006 1:39 PM
To: inform...@iiug.org
Subject: Re: AIX and Informix
We use raw. HACMP folks say use offset 512 - AIX folks say no offset is
needed.
We are going to try some with 512 and see what blows up - or not
Thanks again
Tom
Doug Conrey wrote:
> This prompts me to ask whether you are using raw volumes or some sort of
> cooked space.
>
> DC
>
> > -----Original Message-----
> > From: informix-l...@iiug.org [mailto:informix-list-
> > bou...@iiug.org] On Behalf Of Link, David A. (Omaha)
> > Sent: Friday, October 20, 2006 10:11 AM
> > To: tom...@yahoo.com; inform...@iiug.org
> > Subject: RE: AIX and Informix
> >
> > If memory serves me correctly IBM does write some of the LV data in
> the
> > first 512 bytes of the volume. Now that data is accessed very rawly
> and
> > is written when you issue some system commands which manages the LVs.
> I
> > am not sure which commands.
> >
> > I think when you fail/fall over using HACMP it will rebuild the data
> in
> > the first 512 bytes of the LV. This ends up overwriting your informix
> > data if you don't offset it.
> >
> > I have always used an offset of the LV in AIX.
> >
> > Here is a small document which kind of covers this.
> >
> > http://www.iiug.org/forums/ids/index.cgi/noframes/read/4433
> >
> > You may find more info out on the web.
> >
> > Hope this points you in the correct direction.
> >
> >
> > David
> >
> > -----Original Message-----
> > From: informix-l...@iiug.org
> > [mailto:informix-l...@iiug.org] On Behalf Of tom...@yahoo.com
> > Sent: Friday, October 20, 2006 10:47 AM
> > To: inform...@iiug.org
> > Subject: Re: AIX and Informix
> >
> > Doug
> >
> > yes - Fishy like fresh from the sea
> >
> >
> > Tom
> >
> >
> >
> > Doug Conrey wrote:
> > > This sounds fishy to me. We have plenty of dbspaces with an offset
> of
> > 0
> > > (on 5.2 and 5.3), and have never had any problems with
> > > adding/dropping/using them.
> > >
> > > DC
> > >
> > > > -----Original Message-----
> > > > From: informix-l...@iiug.org [mailto:informix-list-
> > > > bou...@iiug.org] On Behalf Of tom...@yahoo.com
> > > > Sent: Friday, October 20, 2006 9:22 AM
> > > > To: inform...@iiug.org
> > > > Subject: Re: AIX and Informix
> > > >
> > > > Thanks for the comments.
> > > > We are running into several things.
> > > >
> > > > One is that we set the offset of the dbspace to 0. We are being
> told
> > > it
> > > > needs to have an offset of "something" - that AIX wants this for
> the
> > > > volume group management. Our current environ is HP which we have
> > > always
> > > > used an offset of 0 - it has never been an issue. We have our
> > > physical,
> > > > log and root spaces mirrored and there looks to be some kind of
> > > > corruption, according to support. Kinda wondering if the HACMP
> > > > clustering might be involved also but unsure.
> > > > What we are seeing is this: I dropped a large database and when I
> > went
> > > > to check out the spaces using onstat -d pertaining to the space
> the
> > DB
> > > > used to be in, the % used was a negative number. So the total size
> > > free
> > > > is greater than the total size allocated.
> > > >
> > > > Tom
> > > >
> > > >
> > > > Obnoxio The Clown wrote:
> > > > > tom...@yahoo.com said:
> > > > > > Hello
> > > > > >
> > > > > > We are running into some major walls trying to configure and
> use
> > > AIX
> > > > > > 5.3 and Informix v10 with HACMP clustering and Informix HDR.
> AIX
> > > looks
> > > > > > to be very behind the times, as does the clustering piece.
> This
> > is
> > > for
> > > > > > an intended migration of the main "cash cow" application. Does
> > > anyone
> > > > > > run their "important stuff" on AIX ? I have been researching
> and
> > > most
> > > > > > of what I see is people using AIX from years back or they only
> > use
> > > AIX
> > > > > > for smaller apps that they don't have great concerns being
> down.
> > > > > > Comments, Suggestions, Rants or Raves?
> > > > >
> > > > > Personally, I think AIX tin is very good. I can't comment on
> > HACMP,
> > > > other
> > > > > than that I've never met anyone who used ANY clustering software
> > > (HACMP,
> > > > > Sun, Veritas, Compaq) who didn't prefer HDR.
> > > > >
> > > > > --
> > > > > Bye now,
> > > > > Obnoxio
> > > > >
> > > > > "... no bill is required as no value was provided."
> > > > > -- Christine Normile
> > > > >
> > > > > --
> > > > > This message has been scanned for viruses and
> > > > > dangerous content by OpenProtect(http://www.openprotect.com),
> and
> > is
> > > > > believed to be clean.
> > > >
> > > > _______________________________________________
> > > > Informix-list mailing list
> > > > Inform...@iiug.org
> > > > http://www.iiug.org/mailman/listinfo/informix-list
> >
> > _______________________________________________
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> > _______________________________________________
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TBP
> The best practice is leave an offset on AIX logical volume if you use it as
> a raw device for Informix. The reason is the first block is used to host
> information or meta data about the logical volume including the LVID. This
> information is also hosted in the ODM which is a kind on internal database
> that AIX uses to keep information about all it devices (it is also the
> reason why AIX can do many operation online like increase decrease File
> system size and adding disks and volumes online..etc). In normal operation
> AIX will not refer back to the disk or LV to get its meta data because AIX
> already has in the ODM. But with certain maintenance operation and low level
> command, they query those area directly and if it was over written then the
> operation will fail. For example the import of the volume group importvg,
> syncvg synclvodm..and many more commands. I am not 100% sure if IBM
> internally protected this information and actually start after that LVDA
> (logical volume descriptor area) block, but in the older AIX versions that
> was the practice to leave an offset and it was carried forward since then
> (at least for me).
There is NO other O/S that says "Here is a logical volume, and you must
not use the first ??? bytes from it." Why does AIX present this as
"available" when it isn't? So what if it was "historical", it ain't right.
> I have experience in all flavors of Unix and I have to say the AIX is my
> favorite. From my experience with clients it is the most stable and has the
> highest availability (I have a client on AIX 4.3.3 with almost 1000 days of
> uptime, Obviously they did not have to install any patch during this
> period!!?). Non of the other Unix flavors can do maintenance (like kernel
> tuning) dynamically and online.
Wierd, quite a few that I have come across have some "dynamic" tuning
capabilities (HP-UX can do some, Linux can do some etc. etc.).