Re: segments/extents ? maxextents?

Rob Williamson wrote:
>
> Thankyou for the response but could you clarify one area?
>
> MAXEXTENTS
> specifies the total number of extents, including the first, that Oracle
> can allocate for the object. The minimum value is 1 (except for rollback
> segments, which always have a minimum value of 2). The default value
> depends on your data block size.
>
> Which data block size OS or Oracle?
>
> What happens if I leave maxextents out of my storage clause ( I have
> seen this done )but have a min =2 and initial=next=256K and pctincrease
> =0 for RBS will it calculate how many extents I need
> up to my 10 M? ie 37 or some other number?
>
> Could I verify this if I created a tablespace for testing to prove these
> things to myself using dba_extents view and tablespaces view or some
> other views?
>
> How do you find out your OS block size ( or whatever it is that helps
> figure DB_Block_size parameter; they should be multiples correct? 128K
> os block size should have at least 128K
> DB_Block_Size or 256,512,1024 ... ) I use digital unix 4.0.d or e?
>
> Thanks again
> Rob
>
>
>
>
>
> Sybrand Bakker wrote:
> > >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 )
>
> > >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?
> > No
> > >This calcualtion would yield 10M/256K= 37.9 extents or 37 depending on
> > >how the
> > >block size internal rounding would work.
> > >
> > 37 extents
>
> > Sybrand Bakker, Senior Oracle DBA

Most OS's have a block size of 512 or 1024 bytes. Typical Oracle block sizes are 4k or 8k.

If you do not specify maxextents on a table, it will be taken from the defaults nominated with the tablespace (have a look at dba_tablespaces for the info)

hth
connor

-- 
==============================
Connor McDonald

http://www.oracledba.co.uk

"Some days you're the pigeon, some days you're the statue..."