High Water Mark for Undo tablespace..!!

Hello Everybody,
I was searching since long to get how much maximum the undo tablespace might have reached.
Can somebody please help me with the query to find out what is the maximum that undo tablespace has been reached.
Any help will be greatly appreciated.
Thanks -
Harsh.

Hi,
Undo tablespace are different from the normal tablespace. They consist of undo segments which can have undo blocks in three status
1)ACTIVE
This means that undo extent is Active and being currently used by a transaction
2)UNEXPIRED
This represents the extents which are required to satisfy the time specified by Undo_retention Initialisation parameter.
3)EXPIRED
These are extents which are not being used by transaction and have crossed the time specified by Undo_retention .
(http://askoracledba.blogspot.com/2008/04/undo-tablespace-sizing.html)
Now there might be case that the blocks for committed transactions which has passed undo_retention are in middle of datafile.
In case you want HWM information so as to reduce the datafilesize, then I would recommend you to create a new undo tablespace and switch to it. After that you can drop the old undo tablespace.
-Amit
http://askoracledba.blogspot.com

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Actually there's no HWM problem for rollback segment, in 8i and before, you can set the OPTIMAL size of your rollback segment.
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High water mark creates performance degradation

Hi all,
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what were the objects and recommendations generated after Segment Advisor job execution?
SQL> select af.task_name, ao.attr2 segname, ao.attr3 partition, ao.type, af.message
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SQL> select * from v$version;
BANNER
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bi
PL/SQL Release 10.2.0.3.0 - Production
CORE 10.2.0.3.0 Production
TNS for IBM/AIX RISC System/6000: Version 10.2.0.3.0 - Productio
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hi all
Does 'HWML' has any significant role in performance
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hi,
just out of interest this script will tell you each datafile size and its high water mark value.
set serveroutput on
execute dbms_output.enable(2000000);
declare
cursor c_dbfile is
select tablespace_name
,file_name
,file_id
,bytes
from sys.dba_data_files
where status !='INVALID'
order by tablespace_name,file_id;
cursor c_space(v_file_id in number) is
select block_id,blocks
from sys.dba_free_space
where file_id=v_file_id
order by block_id desc;
blocksize binary_integer;
filesize binary_integer;
extsize binary_integer;
begin
/* get the blocksize of the database, needed to calculate the startaddress */
select value
into blocksize
from v$parameter
where name = 'db_block_size';
/* retrieve all datafiles */
for c_rec1 in c_dbfile
loop
filesize := c_rec1.bytes;
<<outer>>
for c_rec2 in c_space(c_rec1.file_id)
loop
extsize := ((c_rec2.block_id - 1)*blocksize + c_rec2.blocks*blocksize);
if extsize = filesize
then
filesize := (c_rec2.block_id - 1)*blocksize;
else
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dbms_output.put_line('.');
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dbms_output.put_line('.');
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dbms_output.put_line('Tablespace: '
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regards
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Explain about high water mark and low watermark

explain about high water mark and low watermark?

biju2012 wrote:
Here are a few links..
http://www.orafaq.com/tuningguide/
Look at Analysing problem SQL > Data Storage Problems > High Water Mark
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:575223085419
I checked both those links, and neither says anything about a "low water mark". One link has a copyright notice of 2003, the other starts with a question about 8.1.6.
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Hi,
What is high water mark in an Oracle data block? I have gone thorugh some material on this, but could not understand fully.
Thanks.

In that case No body can answer anything unless otherwise he is from oracle corp who was involved in development of DB
A copy from other site and pasting here doesnt sound weell but atleast he did a search for you
But your point is valid moreover it seems the OP does not have time to search in google :)

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regards
Sub

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Hi,
These days I am always thinkin' about a question that why Oracle introduces high water mark.
I've found some documents describing this concept, but I still can't make out what's the advantage of the high water mark.
If someone could tell me, I will be very appreciated!

Jaffy wrote:
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:669044239081
regards
Jaffythanks Jaffy, I think I can accept this answer, maybe Oracle takes FTS from HWM as a safe way.
The same thanx to Pavan Kumar and Aman....
----quote from http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:669044239081:
The blocks are in use. The table is a complex data structure, it is not a fifo/lifo queue or
anything like that -- it is a big old heap. Once used -- implies "could still be used".
Edited by: user12977032 on May 14, 2010 12:54 AM

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Hi,
We have large archive gap in standby.
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High Water Mark for Undo tablespace..!!

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