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Tablespace extent management

Dictionary managed

The allocation of extents within the tablespace is managed through the dictionary tables uet$ and fet$.
If the system tablespace is not dictionary managed, it has the following implications:
  • Dictionary managed tablespaces must be read-only
  • New tablespaces must be created as locally managed.
  • The system tablespace cannot be migrated to a dictionary tablespace (for example using dbms_space_admin.tablespace_migrate_to_local.

Locally managed

The allocation of extents within the tablespace is managed through bits (which are stored within the tablespace itself). Each bit corresponds to an extent.

Autoallocate

Oracle will choose extent sizes.

Uniform

All extent sizes within such a tablespace are equal in size.