Overview of Logical Database Structures
The logical storage structures, including data blocks,
extents, and segments, enable Oracle to have fine-grained control of disk space
use.
Tablespaces
A database is divided into logical storage
units called tablespaces,
which group related logical structures together. For example, tablespaces
commonly group together all application objects to simplify some administrative
operations.
Each database is logically divided into one or more tablespaces. One or more datafiles are explicitly created for each tablespace to physically store the data of all logical structures in a tablespace. The combined size of the datafiles in a tablespace is the total storage capacity of the tablespace.
Every Oracle database contains a
Oracle also lets you create bigfile tablespaces. This allows Oracle Database to contain tablespaces made up of single large files rather than numerous smaller ones. This lets Oracle Database utilize the ability of 64-bit systems to create and manage ultralarge files. The consequence of this is that Oracle Database can now scale up to 8 exabytes in size. With Oracle-managed files, bigfile tablespaces make datafiles completely transparent for users. In other words, you can perform operations on tablespaces, rather than the underlying datafiles.
Online and Offline Tablespaces
A tablespace can be online (accessible) or offline (not accessible). A
tablespace is generally online, so that users can access the information in the
tablespace. However, sometimes a tablespace is taken offline to make a portion
of the database unavailable while allowing normal access to the remainder of
the database. This makes many administrative tasks easier to perform.
Tablespaces
A database is divided into logical storage
units called tablespaces,
which group related logical structures together. For example, tablespaces
commonly group together all application objects to simplify some administrative
operations.Each database is logically divided into one or more tablespaces. One or more datafiles are explicitly created for each tablespace to physically store the data of all logical structures in a tablespace. The combined size of the datafiles in a tablespace is the total storage capacity of the tablespace.
Every Oracle database contains a
SYSTEM tablespace and a SYSAUX
tablespace. Oracle creates them automatically when the database is created. The
system default is to create a smallfile tablespace,
which is the traditional type of Oracle tablespace. The SYSTEM and SYSAUX tablespaces are
created as smallfile tablespaces.Oracle also lets you create bigfile tablespaces. This allows Oracle Database to contain tablespaces made up of single large files rather than numerous smaller ones. This lets Oracle Database utilize the ability of 64-bit systems to create and manage ultralarge files. The consequence of this is that Oracle Database can now scale up to 8 exabytes in size. With Oracle-managed files, bigfile tablespaces make datafiles completely transparent for users. In other words, you can perform operations on tablespaces, rather than the underlying datafiles.
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