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Oracle - Difference between a data block, an
extent and a segment - Feb 18, 2010 at 11:00 PM by Rajmeet
Ghai
Explain the difference between a data block, an
extent and a segment.
Data blocks, extent and segments are logical units of data
storage in oracle.
Data block is the optimum level of storage. Also
known as pages, each data block corresponds to a specific number of
bytes.
Extent: The next level is extent containing a
specific number of adjoining data blocks.
Segment: Set of extents forms a segment. These
extents may or may not be adjoining. Space is allocated in units of
one extent. When existing extents of a segment are full, another
extent is allocated.
Oracle -
Difference between a data block, an extent and a segment - April 10, 2009
at 11:00 AM
Explain the difference between a data
block, an extent and a segment.
A data block is the smallest unit of logical
storage for a database object. As objects grow they take chunks of
additional storage that are composed of contiguous data blocks.
These groupings of contiguous data blocks are called extents. All
the extents that an object takes when grouped together are
considered the segment of the database object.
Also read
An extent is stored some specific information. This information
is stored using specific number of adjoining data blocks. A
collection of extent is called as a segment stored in the same
tablespace.............
Tablespace fragmentation can be prevented by using PCTINCREASE
command. PCTINCREASE is the percentage a new subsequent extent will
grow...............
Data blocks are also called logical blocks, Oracle blocks, or
pages. At the finest level of granularity, Oracle stores data in
data blocks.............
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