ADSM-L

Re: Deleting dbvol takes long

2002-12-16 05:27:47
Subject: Re: Deleting dbvol takes long
From: Sheelagh Treweek <sheelagh.treweek AT COMPUTING-SERVICES.OXFORD.AC DOT UK>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Mon, 16 Dec 2002 10:27:40 +0000
Hi Gerhard,

I came across this myself a few weeks ago when I was wanting to
increase the size of the DB vols I use from 2GB to 4GB.  This DB
was 100GB approx and so there were quite a lot of volumes to be
deleted, and also on SSA.  The elapsed time got longer as I did
more volumes.  It started at 20 minutes and was closer to an
hour when the work was all finished - a week later (as I had to
do just some of it each day).  2 hours seems excessive per vol.

Mirroring a volume on the other hand took just 3-4 minutes.  I
did look at iostat on all the disks when I was doing this and
TSM server does seem to write to many volumes when it is doing
deletes of a db-volume.  Whether it is filling in little gaps
or updating multiple tables I wouldn't know - you'd have to
know full details of the internals (and we didn't cover this
scenario at the Oxford Symposium when Dave Cannon presented on
DB internals).  I also observed that if you have multiple new
and empty DB-vols that it wrote to all of them.  It is something
I would like to understand better.

I did think of putting in a PMR to investigate but I needed to get
on and not spend the time, possibly over several weeks getting the
required diagnostics.  In my expereience, this is the sort of TSM
related performance problem that probably wouldn't be resolved very
quickly ...

Best wishes, Sheelagh
--
Sheelagh Treweek
Oxford University Computing Services
Email: sheelagh.treweek AT oucs.ox.ac DOT uk
Phone: +44 (0)1865 273205 Fax:-273275


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Date: Thu, 12 Dec 2002 14:16:20 +0100
From: Gerhard Rentschler <g.rentschler AT RUS.UNI-STUTTGART DOT DE>
Subject: Deleting dbvol takes long
To: ADSM-L AT VM.MARIST DOT EDU

I just deleted a 2GB DB volume. It took 2 hours to complete.
The deleted volume resided on an SSA disk. The server CPU is not a
bottleneck. Can anybody tell me why it is taking so much time? I first hoped
it would do some DB reorg on the fly. But it obviously doesn't.
Best regards
Gerhard

---
Gerhard Rentschler            email:g.rentschler AT rus.uni-stuttgart DOT de
Regional Computing Center     tel.   ++49/711/685 5806
University of Stuttgart       fax:   ++49/711/682357
Allmandring 30a
D 70550
Stuttgart
Germany

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