RE: Tape capacity planning?
Hi,
this is what we use to get it for a single dbspace:
EXEC SQL select (sum(chksize - nfree)) into :spages
from sysdbspaces, syschunks where
sysdbspaces.dbsnum = syschunks.dbsnum and
name = :sname;
against sysmaster database.
There are a couple of things to keep in mind:
- TEMP dbspaces are not backed up/archived, so you
don't want to count their size/usage.
- for a whole system backup (onbar) and all ontape
archives (by default they are "whole system"), those log
records are backed up, that are necessary to roll back
open transactions in case no logs are restored after physical
restore (i.e. no log rollforward).
Depending on amount/length of open transactions at time
of archive (i.e. archive checkpoint) the size of this log data
will vary.
BLOBSpace BLOBs belong to this log record data, so if BLOBs
are involved that can increase the numbers ...
- tape device compression:
always an interesting theme which I tried to explain before ...
In short: already compressed data (think JPEG in BLOBs) often
increases when compressed again (no matter whether compression
is done by hard- or software).
So be cautious with the claims on the tapes/devices regarding
compression efficiency.
Regards,
Martin
--
Martin Fuerderer
IBM Informix Development Munich, Germany
Information Management
owner-informix-list@iiug.org wrote on 23.03.2005 16:05:25:
> Yes, it is a rough estimate - will have to go back to my queries if you
> want more precise info ....
>
>
>
> -----Original Message-----
> From: Darren_Jacobs@carmax.com [mailto:Darren_Jacobs@carmax.com]
> Sent: 23 March 2005 04:28 PM
> To: Dirk Moolman
> Cc: informix-list@iiug.org
> Subject: RE: Tape capacity planning?
>
> Dirk,
>
> Thanks for the response. However, the sum below is more than the total
> allocated in my database. I did perform a sum on systabinfo on
> ti_pagesused and ti_npused and ti_npdata. Does anyone know if this
> would
> reflect the amount being backed up?
>
> BTW, 9.40 FC2 on HPUX 11
>
> Thanks
>
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>
> "Dirk Moolman"
>
> <DirkM@mxgroup.co
>
> .za>
> To
> <Darren_Jacobs@carmax.com>,
>
> 03/23/2005 09:10 <informix-list@iiug.org>
>
> AM
> cc
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> Subject
> RE: Tape capacity planning?
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> On my version of Informix, it is the "used space" in the database chunks
> that gets backed up(would guess that it is the same in the new versions
> as well)
>
> I run a query that calculates this for me, on Informix:
>
> database sysmaster;> select sum(chksize - nfree) * 2048 (2048 for the 2k page size in my
> opsys)
> from syschunks
>
>
>
> -----Original Message-----
> From: owner-informix-list@iiug.org [mailto:owner-informix-list@iiug.org]
> On Behalf Of Darren_Jacobs@carmax.com
> Sent: 23 March 2005 03:12 PM
> To: informix-list@iiug.org; ids@iiug.org
> Subject: Tape capacity planning?
>
> Greetings,
>
> By chance, does any one have a script that will calculate the amount of
> space a backup will use on a tape?
>
> Thanks
>
> sending to informix-list
>
>
> sending to informix-list
sending to informix-list