| high wark mark [message #328944] |
Mon, 23 June 2008 08:18  |
mandygrewalindia
Messages: 14
Registered: February 2008
Location: india
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Junior Member |
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hi I'm beginner in FUNDA one
I have two questions:
1.any one could explain me wht is high water mark...?? I tried to google out too. but could nt get satisfied answer.
2.and while direct loading "all data that is loaded using direct load insert is loaded above high water mark": what does it mean??
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| Re: high wark mark [message #328955 is a reply to message #328952] |
Mon, 23 June 2008 09:20  |
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(say, u have the last row of a table at location 100th)
high water mark arises when the memory doesnt get relaese or the space doesnt get relaesed off after the deletion of the rows from the table.
(this means u are deleting 50 rows from the table: now the memeory doesnt comes back to 50th position, rather than it in 100th)so while next insertion, the new data get inserted from the original level from the 100th position rather from 50th position , which encounter with performance issuse.
To avoid high water mark ,just move the particular table to another tablespace n vice -versa.
you can now search the google to get the scripts for finding the high water mark.
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| Re: high wark mark [message #328959 is a reply to message #328955] |
Mon, 23 June 2008 09:38 |
JRowbottom
Messages: 5933
Registered: June 2006
Location: Sunny North Yorkshire, ho...
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Senior Member |
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Ummmm.......no.
The High Watermark is not related to re-use of deleted space in a table.
The high Water Mark is the last block to be allocated to a table that has had data in it. When Oracle performs a Full Table Scan, it reads all the blocks allocated to the table that have had data in them at some point.
Eg:
You have a large number of rows in a table.
You delete all of them and then insert a small number of rows.
The second set of rows will get inserted at the start of the table, but a full table scan will still have to read all the blocks that previously had data in them.
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