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Home -> Community -> Mailing Lists -> Oracle-L -> RE: How does Oracle set the High Water Mark?
Good answer.
On mine it's set to 0. I think this is a feature of Automatic Space Segment
Management (see other post).
Thanks
Ray
-----Original Message-----
From: Tim Gorman [mailto:tim_at_sagelogix.com]
Sent: Wednesday, March 10, 2004 2:13 PM
To: oracle-l_at_freelists.org
Subject: Re: How does Oracle set the High Water Mark?
Used to be controlled by a hidden parameter named:
PARAMETER DESCRIPTION DFLT
--------------------------------------- -------------------- -----
_bump_highwater_mark_count = 0 how many blocks TRUE
should we allocate
per free list on
advancing HW
And it used to default to 5. But, on my 9.2.0.1 database, it doesn't appear to have a default value at all. If it is being calculated internally, then on your database it seems to be 13, perhaps?
on 3/10/04 6:56 AM, Feighery Raymond at Raymond.Feighery_at_churchill.com wrote:
> Oracle 9.2.0.4 Solaris 8
>
> How does Oracle set the HWM? In the example below, I create a table and
> insert one row. I would expect only one block to be used, instead Oracle
> seems to have pushed the HWM up to 13 blocks. I can imagine that this
might
> be done to "pre-mark" rows as used during bulk inserts, but how does
Oracle
> decide where to set the HWM?
>
> SQL> select * from dba_tablespaces where tablespace_name = 'EXAMPLE';
> TABLESPACE_NAME BLOCK_SIZE INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS
> ------------------------------ ---------- -------------- -----------
> -----------
> MAX_EXTENTS PCT_INCREASE MIN_EXTLEN STATUS CONTENTS LOGGING FOR EXTENT_MAN
> ----------- ------------ ---------- --------- --------- --------- ---
> ----------
> ALLOCATIO PLU SEGMEN DEF_TAB_
> --------- --- ------ --------
> EXAMPLE 4096 65536 1
> 2147483645 65536 ONLINE PERMANENT LOGGING NO LOCAL
> SYSTEM NO AUTO DISABLED
>
> SQL> create table t (col1 number(1));
> Table created.
> SQL> analyze table t compute statistics;
> Table analyzed.
> SQL> insert into t values(1);
> 1 row created.
> SQL> commit;
> Commit complete.
> SQL> select blocks, empty_blocks from user_tables where table_name = 'T';
> BLOCKS EMPTY_BLOCKS
> ---------- ------------
> 0 16
> SQL> analyze table t compute statistics;
> Table analyzed.
> SQL> select blocks, empty_blocks from user_tables where table_name = 'T';
> BLOCKS EMPTY_BLOCKS
> ---------- ------------
> 13 3
>
>
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