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Re: segments/extents ? maxextents?

From: Howard J. Rogers <howardjr_at_www.com>
Date: Tue, 16 Oct 2001 07:02:20 +1000
Message-ID: <3bcb4eb3@news.iprimus.com.au>


Check out the Administration tips on my site. There are papers there on sizing rollback segments, and on the "right" number of extents for segments.

Regards
HJR

--
Resources for OracleT: www.geocities.com/howardjr2000
=========================================


"Rob Williamson" <robw_at_physics.umd.edu> wrote in message
news:3BC9F7C3.BB67CB2B_at_physics.umd.edu...

> Two questions that relate to Tablespace and Table creation:
>
> The manuals say not to create an rollback segment tablespace with
> unlimited
> maxextents. So what do I choose and why? What about initaial and next?
> For a small database <500M I was imagining a 10M datafile with
> default storage (initial 256K next 256K minextents 2 maxextents 4096
> pctincrease 0 )
> Does this mean that my RB segments are 256K
> or each extent is 256K or both?
> Do you figure out the max size of a rollback segment by initial x
> maxextents ?
> In which case 4096 would be larger than 10M
> so then I could figure out maxextents by filesize / initial ( as long as
> next is the same
> and pctincrease = 0 )? Is this wrong?
> This calcualtion would yield 10M/256K= 37.9 extents or 37 depending on
> how the
> block size internal rounding would work.
>
> This question actually led me to question #2 which is when you
> create a table what is the size of the segment?
> I have heard that you should try ( but not too hard to get your tables
> or objects (
> especially static tables) into one segment which if what I said above is
> true
> for a 1M static table I would want the storage clause for the table to
> be
> storage clause ( initial 1M next 256k pctincrease 0 minextents 1
> maxextents 4 )
> This would allow the table to double in size up to 2M?
>
> Am I way off with this stuff the Oracle 8i DBA handbook is good but only
> if you really understand the guts of oracle which I am attempting to do.
>
> I guess to summarize:
> Is intial the size of your segment?
> Does does initial + ( maxextent * next ) < datafile size make sense
> And how do you decide on the RBS initial & max
>
> Does DB_Block_Size get figured into any of this?
>
> Thanks for any help in advance.
>
> Rob
Received on Mon Oct 15 2001 - 16:02:20 CDT

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