Most probable use of an extent - Minimize the amount of wasted (empty) storage - Oracle Architecture

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• Nirja Shah   -Posted on 27 Aug 15
  -The most probable use of an extent is to minimize the amount of wasted (empty) space.
  
  -Extents - They are the building blocks of segments; in turn, they consist of data blocks.
  -An extent is used to minimize the amount of wasted (empty) storage. As more and more data is entered into tablespaces in your database, the extents used to store that data can grow or shrink as necessary.
  -In this manner, many tablespaces can share the same storage space without preallocating the divisions between those tablespaces.
  
  - Segment - It has four types of segment they are:
  
  -Rollback segment - It stores rollback information used when data must be rolled back.
  -Data segment - It stores user data within the database.
  -Index segment - Stores indexes.
  -Temporary segment - Created when a SQL statement needs a temporary work area; these segments are destroyed when the SQL statement is finished. These segments are used during various database operations, such as sorts.

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