by corky.. » Sun, 31 Dec 1899 09:00:00
1. How exactly does oracle calculate the size of the next extent it
will allocate in a segment? formula?
2. I also see segments not following the next_extents value set for
that segment...instead it follows the next_extent value specified for
the tablespace's default...why's that happen?
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by Michel Cado » Sun, 31 Dec 1899 09:00:00
When Oracle allocates a new extent it calculates the "next next":Quote:>dear sirs 'n ma'ams,
>1. How exactly does oracle calculate the size of the next extent it
>will allocate in a segment? formula?
May be the parameters NEXT and PCTINCREASE were not given at theQuote:>2. I also see segments not following the next_extents value set for
>that segment...instead it follows the next_extent value specified for
>the tablespace's default...why's that happen?
Quote:>Sent via Deja.com http://www.deja.com/
>Share what you know. Learn what you don't.
by markp7.. » Sun, 31 Dec 1899 09:00:00
I would just like to add: remember also that the the value of theQuote:> >dear sirs 'n ma'ams,
> >1. How exactly does oracle calculate the size of the next extent it
> >will allocate in a segment? formula?
> When Oracle allocates a new extent it calculates the "next next":
> new NEXT = old NEXT * (1+PCTINCREASE/100)
> this value is rounded up to the next multiple of 5 blocks.
> >2. I also see segments not following the next_extents value set for
> >that segment...instead it follows the next_extent value specified for
> >the tablespace's default...why's that happen?
> May be the parameters NEXT and PCTINCREASE were not given at the
> creation of the table and the table have been altered after with
> the parameters NEXT and/or PCTINCREASE you see now.
--
Mark D. Powell -- The only advice that counts is the advice that
you follow so follow your own advice --
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by corky.. » Sun, 31 Dec 1899 09:00:00
Again Thanks,
Corky
(an aspiring DBA)
= )
> > >1. How exactly does oracle calculate the size of the next extent it
> > >will allocate in a segment? formula?
> > When Oracle allocates a new extent it calculates the "next next":
> > new NEXT = old NEXT * (1+PCTINCREASE/100)
> > this value is rounded up to the next multiple of 5 blocks.
> > >2. I also see segments not following the next_extents value set for
> > >that segment...instead it follows the next_extent value specified
for
> > >the tablespace's default...why's that happen?
> > May be the parameters NEXT and PCTINCREASE were not given at the
> > creation of the table and the table have been altered after with
> > the parameters NEXT and/or PCTINCREASE you see now.
> I would just like to add: remember also that the the value of the
> next_extent column in dba_tables is recalculated each time an extent
> allocation takes place (after the first) to show the new next extent
> value and does not reflect the size of the extent just allocated
> whenever pctincrease is not set to zero.
> --
> Mark D. Powell -- The only advice that counts is the advice that
> you follow so follow your own advice --
> Sent via Deja.com http://www.deja.com/
> Share what you know. Learn what you don't.
1. next extent-, exist extent-question
Hi,
in a manual I read that the following queries should
be executed weekly:
PROMPT Find tables that don't match the tablespace default for NEXT
extent.
PROMPT The imlicit rule here is that every table in a given tablespace
PROMPT should use the exact same value for NEXT, which should also be
the
PROMPT tablespace's default value for NEXT.
PROMPT
PROMPT This tells us what the setting for NEXT is for these objects
today.
SELECT segment_name, segment_type, ds.next_extent as Actual_Next,
dt.tablespace_name, dt.next_extent as Default_Next
FROM dba_tablespaces dt, dba_segments ds
WHERE dt.tablespace_name = ds.tablespace_name
AND dt.next_extent != ds.next_extent
AND ds.owner = 'SCOTT'
ORDER BY tablespace_name, segment_type, segment_name;
--------------------------------------------------------
PROMPT This tells us how many of each objects extents differ in size
from
PROMPT the tablespace's default size. If this report shows a lot of
PROMPT different sized extents, the free space is likely to become
PROMPT fragmented. If so, this tablespace has to be reorganized.
PROMPT
SELECT segment_name, segment_type, count(*) as nr_exts,
sum(DECODE(dx.bytes,dt.next_extent,0,1)) as nr_illsized_exts,
dt.tablespace_name, dt.next_extent as dflt_ext_size
FROM dba_tablespaces dt, dba_extents dx
WHERE dt.tablespace_name = dx.tablespace_name
AND dx.owner = 'SCOTT'
GROUP BY segment_name, segment_type, dt.tablespace_name, dt.next_extent;
My question is: Both queries return a lot of rows. What do I have
to do, to fix it?
Thanx in advance
Michael
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