What is Water Mark in Oracle?
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Answer / nithya
High water mark(hwm) indicates the max level to
which the data has risen in the table. when data is inserted
in the table hwm is adjusted accordingly, If all data is
deleted in a table, hwm is not adjusted and remains pointing
to the max data position in the table.
| Is This Answer Correct ? | 22 Yes | 1 No |
Answer / bikash khuntia
High watermark means, the largest amouth of data
that was placed in a table. for example, Let's say
you created a table and inserted 100 records, and then
added 1000 records more. Now the table highwater mark is
the 1000 record. Now let's say you deleted all the
records in that table using the 'delete' command. Now
your highwater mark for the table still sits at the 1000
record . Though after the delete you have no records
in the table, when a query is performed on this empty
table, it will still scan upto the 1000 highwater mark,
So even with no records, the query will still take
sometime returning because it scans up to the high
watermark.
Now, instead of deleating the records with delete command,
You trucate the tabel, Truncate will remove the high
watermark for the table, and now on an empty table the
query is faster due to the high watermark being gone
| Is This Answer Correct ? | 21 Yes | 0 No |
Answer / raya tharaka ram
The initial position of the high water mark is extent 0
block 0 for tables and extent 0 block 1 for indexes.
| Is This Answer Correct ? | 14 Yes | 4 No |
Answer / anks
This is a term used with table segments stored in the
database. If you envision a table, for example, as a 'flat'
structure or as a series of blocks laid one after the other
in a line from left to right, the high-water mark (HWM)
would be the rightmost block that ever contained data.
| Is This Answer Correct ? | 9 Yes | 6 No |
Answer / firdos kashmiri
High water mark is just a line separates the used blocks and free blocks, the blocks above hwm are free blocks and are ready to use and blocks below hwm are used blocks.
| Is This Answer Correct ? | 0 Yes | 0 No |
Answer / nihar ranjan manadhata
This is a term used with table segments stored in the
database. If you envision a table, for example, as a 'flat'
structure or as a series of blocks laid one after the other
in a line from left to right, the high-water mark (HWM)
would be the rightmost block that ever contained data.
| Is This Answer Correct ? | 2 Yes | 7 No |
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