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Lesson 5Oracle Extents
ObjectiveWhat is the role of Oracle extents?

Role of Oracle extents Data

Each segment is composed of extents, which are groups of contiguous data blocks.
Oracle manages the use of extents, allocating a new one when one is full.

Extent Size

You can specify the size of an extent for a database object with the CREATE command for the object, or alter the size of subsequent extents with the ALTER command for the object.
When you first create a database table, Oracle allocates an initial extent for the segment. If the data in the table gets too large to fit in the initial extent, Oracle allocates a new one. The FlipBook below illustrates how this happens.

Oracle Extent Allocation
The incremental extent can be the same size as the initial extent, or you can indicate that each subsequent extent must be a certain percentage larger than the previous extent. For example, you could indicate that each subsequent extent must be 50% larger than the previous one.
You can also specify the minimum and maximum number of extents. The minimum number of extents controls how many extents are initially allocated when you create the object. If you specify a maximum number of extents, it has the effect of limiting the size of the table.
The next lesson shows how to set extent parameters for database objects.

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