And this only matters for queries for data dictionary views. I also beleave
that number of extents matter if you have parallel processing. I saw
something about it on Johnathan Lewis web site.
Alex Hillman
-----Original Message-----
Sent: Thursday, June 28, 2001 8:36 AM
To: Multiple recipients of list ORACLE-L
Rachel,
That maximum isn't a hard limit. Oracle themselves impose no limit of this
kind.
After you use all of the available space in the segment header block, any
additional space map entries are overflowed into additional extent maps
within
the segment.
This means that because the used extent information isn't cached in the data
dictionary, queries against dba_extents etc. can cause many blocks to be
read
from LMTs if the map entries have overflowed in this manner.
Therefore, the limitation is more of a recommendation to ensure that good
performance is maintained.
Regards,
Mike
|--------+----------------------->
| | "Rachel |
| | Carmichael" |
| | <carmichr@hot|
| | mail.com> |
| | |
| | 06/28/01 |
| | 10:46 AM |
| | Please |
| | respond to |
| | ORACLE-L |
| | |
|--------+----------------------->
>-------------------------------------------------------------------|
| |
| To: Multiple recipients of list ORACLE-L |
| <[EMAIL PROTECTED]> |
| cc: (bcc: Mike Hately/ETECH) |
| Subject: Re: Fragmentation & Locally Managed Tablespaces|
>-------------------------------------------------------------------|
so we are going back to the Oracle specified maximum extents for a
particular blocksize?
>From: Paul Drake <[EMAIL PROTECTED]>
>Reply-To: [EMAIL PROTECTED]
>To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
>Subject: Re: Fragmentation & Locally Managed Tablespaces
>Date: Thu, 28 Jun 2001 00:15:50 -0800
>
>VIVEK_SHARMA wrote:
> >
> > Is Fragmentation of Objects meaningless in Locally managed Tablespaces
> > Assuming EXTENTS is 3,000 for Some of the Objects
> >
> > Or Do the Objects need to be DE-Fragmented using exp/imp ?
> >
>
>Vivek,
>
>funny, I was just looking into this tonight.
>
>what is your block size?
>
>I would recommend a quick visit to our friend Steve Adams site:
>
>http://www.ixora.com.au/tips/creation/extents.htm
>
>"For this reason, we recommend that the number of extents per segment in
>locally managed tablespaces be limited to the number of rows that can be
>accommodated in the extent map within the segment header block
>- that is, approximately (db_block_size / 16) - 7."
>
>for an 8 KB block size - that is 505 extents per segment.
>
>Those objects would be good candidates to move to a different (new?)
>tablespace with a larger (uniform) extent size.
>
>Paul
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