The Oracle DBA_TABLESPACES view provides comprehensive insights into all tablespaces within the database. Unlike the USER_TABLESPACES view, which focuses solely on tablespaces accessible to the current user, DBA_TABLESPACES encompasses both system-defined and user-defined tablespaces.

It’s essential to understand that DBA_TABLESPACES is a view, not a table. Therefore, the data it presents are not directly stored within it but rather retrieved from other underlying tables within the database.

Column 

The view presents several columns, each offering valuable information about the tablespaces:

  • TABLESPACE_NAME: This column provides the name of the tablespace, encompassing both system and user-defined tablespaces;
  • BLOCK_SIZE: Specifies the block size associated with the tablespace;
  • INITIAL_EXTENT: Indicates the default size of the initial extent for objects within the tablespace;
  • NEXT_EXTENT: Represents the default size for incremental extents within the tablespace;
  • MIN_EXTENTS: Specifies the default minimum number of extents for objects within the tablespace;
  • MAX_EXTENTS: Indicates the default maximum number of extents for objects within the tablespace;
  • PCT_INCREASE: Represents the default percent increase for extent size within the tablespace;
  • MIN_EXTLEN: Specifies the minimum extent size for the tablespace;
  • STATUS: Describes the status of the tablespace, which can be ONLINE, OFFLINE, or READ ONLY;
  • CONTENTS: Indicates whether the tablespace contains permanent or temporary data;
  • LOGGING: Specifies the default logging attribute for the tablespace;
  • FORCE_LOGGING: Indicates whether the tablespace operates under force logging mode;
  • EXTENT_MANAGEMENT: Describes the extent management tracking, which can be DICTIONARY or LOCAL;
  • ALLOCATION_TYPE: Specifies the type of extent allocation in effect for the tablespace;
  • PLUGGED_IN: Indicates whether the tablespace is plugged in;
  • SEGMENT_SPACE_MANAGEMENT: Describes how free and used segment space within the tablespace is managed;
  • DEF_TAB_COMPRESSION: Indicates whether default table compression is enabled;
  • RETENTION: Specifies the undo tablespace retention policy;
  • BIGFILE: Indicates whether the tablespace is a bigfile or smallfile tablespace.

Example Queries

To retrieve information from the DBA_TABLESPACES view, SQL queries can be constructed. For instance, the following query lists all tablespaces:

sql

SELECT * FROM DBA_TABLESPACES;

Another example demonstrates querying for tablespaces with names starting with ‘AG’:

sql

Copy code

SELECT tablespace_name, logging, status, contents, extent_management, allocation_type, initial_extent/1024 init_ext_kb, next_extent/1024 next_ext_kb, pct_increase, min_extents, max_extents/1024 max_ext_db, min_extlen FROM DBA_TABLESPACES WHERE tablespace_name LIKE 'AG%' ORDER BY 1;

Conclusion

Understanding the structure and contents of the DBA_TABLESPACES view is essential for efficiently managing tablespaces within an Oracle database environment. By leveraging this view, administrators can gain valuable insights into tablespaces, facilitating effective database management and optimization efforts.

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