You need to benchmark ASSM carefully because it may
have impact especially on your smaller tables. To
avoid the concurrency issues, you can end up with
blocks "sprayed" as rows are created. For example,
you might add a single row to an (empty) table and end
up with the table being 10 blocks instead of 1 because
ASSM tries to spread blocks around in this fashion.
If those tables are targets of joins ( to large
tables) as they often tend to be in DW, you might be
trawling through a much larger amount of blocks then
you need to be...
hth
connor
- Rachel Carmichael <wisernet100_at_yahoo.com> wrote:
> Thanks Ian, that was indeed the question, although
> the other
> information is useful as well.
>
> if I understand what you are saying correctly, it
> works but it won't
> really buy me anything and I might do better
> controlling the space
> myself. And while you have had no problems, you've
> heard negative
> things about it. I can't afford to have this
> database not be available
> so I'll manage them on my own
>
> Rachel
>
> --- "MacGregor, Ian A." <ian_at_SLAC.Stanford.EDU>
> wrote:
> > The question posed was not whether "extent
> management local" should
> > be used, but whether automatic segment space
> management should be
> > used.
> >
> > As this is a data warehouse, I would not expect
> you to have
> > transactions trying to change the same block.
> Assuming you are
> > loading; that is, inserting data and not doing
> updates, wouldn't you
> > try to cram as much data as possible into a block?
> Seems this could
> > be done more easily by controlling these
> parameters yourself
> >
> > I've got one system using automatic segment space
> management without
> > any problems, however when I posed the same
> question on using it a
> > few months ago, the respone which trickled in way
> highly negative
> > concerning its usage.
> >
> > Ian MacGregor
> > Stanford Linear Accelerator Center
> > ian_at_slac.stanford.edu
> >
> > -----Original Message-----
> > Sent: Tuesday, September 03, 2002 8:49 AM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > time for me to ask the experts again.
> >
> > My data warehouse will be 9.2, with all locally
> managed tablespaces.
> > We
> > will be following what I have taken to calling the
> "Goldilocks"
> > principle -- that of small, medium and large
> tablespace extent sizes,
> > with variations in that we will separate indexes
> and data, and will
> > have even more separation for our fact tables into
> partitioned tables
> > and tablespaces.
> >
> > However, now comes the time for me to work out
> storage clauses. And a
> > quick read through the docs leaves me wondering if
> I should just turn
> > on automatic segment-space management and not
> worry about setting
> > PCTFREE, PCTUSED and FREELIST parameters. I can't
> find any real
> > information or bugs on MetaLink either.
> >
> > Does anyone have any experience, good OR bad, with
> using this
> > feature?
> > If you are doing data warehouse work, what are
> good values for the
> > parameters if I DO use them? One fact table is
> likely to be highly
> > updated (customer info) as we collect more and
> more specific
> > information from customers. The rest will be, as
> you would expect
> > from
> > a DW, mostly inserts.
> >
> > Help?
> >
> > Thanks!
> >
> > Rachel
> >
> > __________________________________________________
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> > --
> > Please see the official ORACLE-L FAQ:
> http://www.orafaq.com
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> > Author: Rachel Carmichael
> > INET: wisernet100_at_yahoo.com
> >
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> > INET: ian_at_SLAC.Stanford.EDU
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> __________________________________________________
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> Author: Rachel Carmichael
> INET: wisernet100_at_yahoo.com
>
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Received on Wed Sep 04 2002 - 05:08:22 CDT
