question about dms raw

Jeremy Schleicher

question about dms raw
We are thinking about using dms raw for our databases on AIX and
being one that has no experience with dms raw and only a little more about
unix, I have some questions that I hope someone out there in db2 land can
answer. If you specify a device in your create tablespace statement and
specify say only 10000 pages with lets say that equals about 500 megs just
for the sake of numbers. And lets say that after that I have 500 megs free
on that device, can I use that is apart of another raw device or is that
space now unusable by anything else? I was under the impression that if
you specify a raw device then nothing else can use that device but db2 and
only for that tablespace container. Additionaly, we have our database that
consists of say 6 tablespaces (I know not the right way to do it, but they
did not listen to me) those tablespaces are stripped accross the same 10
devices, is that still possible with DMS raw? Any ideas on how I would
move my database from there current mixture of dms and sms tablespaces to a
database that is just dms raw, other than using the db2move utility (which
would take forever to move 25 gigs worth of data).


Thanks

Jeremy Schleicher
Database System Administrator
May Department Stores Company.



Fabrizio Napolitano

Re: question about dms raw
(in response to Jeremy Schleicher)
Hi Jeremy,

quickly:

>if you specify a device in your create tablespace statement and
>specify say only 10000 pages with lets say that equals about 500 megs
just
>for the sake of numbers. And lets say that after that I have 500 megs
free
>on that device, can I use that is apart of another raw device or is that
>space now unusable by anything else?

When you specify a device in the create tablespace statement then if you
use that device
partially the other space will be wasted, the unused space cannot be used
nor by other
tablespaces nor by other application.
But, there is always a but, depending on your definition of device you can
be able to use all
the space or not. I try to explain myself a bit: if by device you mean a
Physical Drive than
other problems arise. You can't assign a Physical Volume (as called on
AIX) during the create tbs command.
What you can assign in the create command is a Logical device (look at
mklv command or in smitty at the Logical Volume,LV, the AIX name, window)
. Then you can create multiple Logical Volume on a Physical Volume.
Please refer to AIX documentation for more details.

>Additionaly, we have our database that
>consists of say 6 tablespaces (I know not the right way to do it, but
they
>did not listen to me) those tablespaces are stripped accross the same 10
>devices, is that still possible with DMS raw?

I do think you use device here as disk drive, then the answare is yes:
simply you have
to create one LV per device for each of your tablespaces.

>Any ideas on how I would
>move my database from there current mixture of dms and sms tablespaces to
a
>database that is just dms raw, other than using the db2move utility
(which
>would take forever to move 25 gigs worth of data).

I think db2move is the only way to move from SMS tablespaces to DMS one,
but maybe someone can contraddict me.
Depending on the box you are using and on your disks it will take less or
more time. But are you using LOAD or import in the db2move command?
what do you mean with forever?

Hope this help
Fabrizio





Jeremy Schleicher <[login to unmask email]>
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01/16/2003 10:06 PM
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Subject: question about dms raw


We are thinking about using dms raw for our databases on AIX and
being one that has no experience with dms raw and only a little more about
unix, I have some questions that I hope someone out there in db2 land can
answer. I I was under the impression that if
you specify a raw device then nothing else can use that device but db2 and
only for that tablespace container. Additionaly, we have our database
that
consists of say 6 tablespaces (I know not the right way to do it, but they
did not listen to me) those tablespaces are stripped accross the same 10
devices, is that still possible with DMS raw? Any ideas on how I would
move my database from there current mixture of dms and sms tablespaces to
a
database that is just dms raw, other than using the db2move utility (which
would take forever to move 25 gigs worth of data).


Thanks

Jeremy Schleicher
Database System Administrator
May Department Stores Company.



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