• Logical Database Structure

    Logical Database Structure 27.08.2008 No Comments
    1. Blocks
      - similar to a filesystem block. Controllable via the DB_BLOCK_SIZE initialization parameter.
    2. Extents
      - a certain number of contiguous blocks used to store the same piece of data.
    3. Segments
      - collection of extents. Some of the extents making up the segment may belong to different physical datafiles, but are all part of the same tablespace (below).
    4. Tablespaces
      - each database is divided into logical storage units called ‘tablespaces’. The default is to have many small files (smallfile tablespace) to store the tablespace data, but you can also create ‘bigfile’ tablespaces so all of the tablespace data is stored in a single LARGE file.
      - a tablespace can be ‘readonly’ or taken offline independently of the rest of the database.