Re: RE: Tablespace management.

i read some oracle documentation that recommends you keep the number of extents below 1024.

do you feel that this is inaccurate in an LMT? What if Im stuck with dictionary tablespacse and am not allowed to change? Does it matter? I do keep all my extents uniform. I thought there were issuse with contention on FET$ and UET$ in dictionary managed tablespaces for a transaction database?

or am I just wrong?
>
> From: "Cary Millsap" <cary.millsap_at_hotsos.com>
> Date: 2003/05/30 Fri PM 12:55:06 EDT
> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> Subject: RE: Tablespace management.
>
> Wow.
>
> Maybe someone on the list has the time and motive to construct a test to
> determine how many extents for a segment in a ULMT are "bad." My guess from
> some tests we did a couple of years ago is that it will take hundreds of
> thousands of extents before even DROP performance will suffer. And I can't
> think of *anything* that would make having even hundreds of millions of
> extents a bad idea for INSERTs, UPDATEs, MERGEs, or DELETEs. The only
> possible downsides of huge numbers of extents that I can think of are
> perhaps:
>
> * During the INSERT, UPDATE, or MERGE, what is the overhead of the actual
> allocation of the ULMT extent? (This actually may have nothing to do with
> how many extents are already there.)
>
> * During checkpoints on RAC systems, does the number of extents matter the
> way it did when Jonathan Lewis showed a problem with DMT and OPS a few years
> ago?
>
> * Does a huge bitmap section in the head of a data file cause any
> performance problems for backup and recovery?
>
> Aside from that, I can't imagine any more downside of huge numbers of ULMT
> extents than there is from having the Unix filesystem extents that most of
> us have right now and never notice.
>
>
> Cary Millsap
> Hotsos Enterprises, Ltd.
> http://www.hotsos.com
>
> Upcoming events:
> - Hotsos Clinic 101 in Reykjavik, Ottawa, Dallas, Washington, Denver, Sydney
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>
> -----Original Message-----
> Sent: Friday, May 30, 2003 8:50 AM
> To: Multiple recipients of list ORACLE-L
>
> Jared,
>
> It's rather simple. If you follow the rules of third normal form
> you have a table with a certain number of rows, a second with a certain
> number of rows for each row in the first table. Obviously the second table
> needs more space than the first. Now if you use Dictionary management you
> can set the storage parameters of each table individually. But if your
> using local management they both have the same extent sizes. This leads one
> to having the extent sizes smaller to accommodate the first table and large
> numbers of extents for the second table. True fragmentation, namely those
> small useless extents that land between larger used extents, is eliminated
> in local management but then I have not had those problems with dictionary
> management either, unless someone makes the case for moving a table but
> that's very rare.
>
> Dick Goulet
> Senior Oracle DBA
> Oracle Certified 8i DBA
>
> -----Original Message-----
> Sent: Thursday, May 29, 2003 8:25 PM
> To: ORACLE-L_at_fatcity.com
> Cc: Goulet, Dick
> Importance: High
>
>
> Dick,
>
> I'm trying to follow your line of thought, but I think I missed the path.
>
> Objects may not have the same storage requirements, but what does that
> matter?
>
> The only way I can make sense of what you say is if trying to have all
> objects
> occupy a single extent, and there's not much point in that.
>
> Jared
>
>
>
>
>
>
> "Goulet, Dick" <DGoulet_at_vicr.com>
> Sent by: root_at_fatcity.com
> 05/29/2003 03:51 PM
> Please respond to ORACLE-L
>
>
> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> cc:
> Subject: RE: Tablespace management.
>
>
> Thomas,
>
> With the exception of temp and rollback tablespaces I
> have not user locally managed tablespaces just because all objects must
> have the same sized extents. I do not see most tables sharing an equal
> need for storage and using dictionary management allows one to do that, at
> a cost I'll admit, but one that is much easier to swallow.
>
> Dick Goulet
> Senior Oracle DBA
> Oracle Certified 8i DBA
>
> -----Original Message-----
> Sent: Thursday, May 29, 2003 3:25 PM
> To: Multiple recipients of list ORACLE-L
>
>
>
> After reading the documents I've recommended using LOCAL, UNIFORM, AUTO as
> the options for tablespace management. Does anyone have any bad
> experiences with these? AUTOALLOCATE seems to come up with extents that
> are much smaller than I want and MANUAL segment management requires the
> use
> of FREELISTs (and I know that there are problems with freelists freeing up
> space correctly, especially in a parallel environment).
>
> I can't find any basis for making a decision between UNDO and ROLLBACK
> SEGMENTS. Does anyone have any experience or recommendations about UNDO
> usage?
>
> The database will be a materialize view replication of a transaction
> master
> that is being used for decision support and has a 15 minute update/refresh
> cycle. Basically, people can run queries against the snapshot without
> impacting the master.
>
>
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