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Using Oracle Blocks Efficiently

After completing this lesson, you should be able to do the following: Use automatic segment space management Use manual segment space management Manage extents and Oracle blocks Ensure effective use of space Determine the high-water mark Describe the use of Oracle block parameters Recover space from sparsely populated segments Describe and detect chaining and migration of Oracle blocks Perform index reorganization | Using Oracle Blocks Efficiently Objectives After completing this lesson, you should be able to do the following: Use automatic segment space management Use manual segment space management Manage extents and Oracle blocks Ensure effective use of space Determine the high-water mark Describe the use of Oracle block parameters Recover space from sparsely populated segments Describe and detect chaining and migration of Oracle blocks Perform index reorganization Database Storage Hierarchy Tablespace Segments Blocks Extents Extents Extents Space Management The efficient management of space in the database is important to its performance. This section of the lesson examines how to manage extents and blocks in the database. Blocks In an Oracle database, the block is the smallest unit of data file I/O and the smallest unit of space that can be allocated. An Oracle block consists of one or more contiguous operating system blocks. Extents An extent is a logical unit of database storage space . | Using Oracle Blocks Efficiently Objectives After completing this lesson, you should be able to do the following: Use automatic segment space management Use manual segment space management Manage extents and Oracle blocks Ensure effective use of space Determine the high-water mark Describe the use of Oracle block parameters Recover space from sparsely populated segments Describe and detect chaining and migration of Oracle blocks Perform index reorganization Database Storage Hierarchy Tablespace Segments Blocks Extents Extents Extents Space Management The efficient management of space in the database is important to its performance. This section of the lesson examines how to manage extents and blocks in the database. Blocks In an Oracle database, the block is the smallest unit of data file I/O and the smallest unit of space that can be allocated. An Oracle block consists of one or more contiguous operating system blocks. Extents An extent is a logical unit of database storage space allocation consisting of a number of contiguous data blocks. One or more extents make up a segment. When the existing space in a segment is completely used, the Oracle server allocates a new extent for the segment. Segments A segment is a set of extents that contains all the data for a specific logical storage structure within a tablespace. For example, for each table, the Oracle server allocates one or more extents to form data segments for that table. For indexes, the Oracle server allocates one or more extents to form its index segment. Allocation of Extents To avoid the disadvantages of dynamic extent allocation: Create locally managed tablespaces. Size the segments appropriately. Monitor segments ready to extend. Allocation of Extents When database operations cause the data to grow and exceed the space that is allocated, the Oracle server extends the segment. Dynamic extension or extending the segment when executing an INSERT or UPDATE statement reduces performance because the server