Locally managed (LMT) vs. Dictionary managed (DMT) tablespace

来源:这里教程网 时间:2026-03-03 11:37:57 作者:
The LMT is implemented by adding the extent management local clause to the tablespace definition syntax. Unlike the older dictionary managed tablespaces (DMTs), LMTs automate extent management and keep the Oracle DBA from being able to specify the next storage parameter to govern extent sizes. The only exception to this rule is when NEXT is used with minextents at table creation time.


 


In a dictionary managed tablespace (DMT), the data dictionary stores the free space details.  While the free blocks list is managed in the segment heard of each table, inside the tablespace), the Free space is recorded in the sys.uet$ table, while used space in the sys.uet$ table. 


 


But with high DML-rate busy tablespaces the data dictionary became a I/O bottleneck and the movement of the space management out of the data dictionary and into the tablespace have two benefits.  First, the tablespace become independent and can be transportable (transportable tablespaces).  Second, locally managed tablespaces remove the O/O contention away from the SYS tablespace.


Segment size management manual vs segment size management auto.


 


Here is how to migrate the SYSTEM tablespace from dictionary managed to local managed.


 


< Code   2.20 - dbms_space_admin_mig_to_local.sql




conn pkg/pkg#123


--How to migrate SYSTEM tablespace from dictionary managed to locally managed


--Check if you have temporary tablespace other than SYSTEM


col file_name for a40


select


   file_name,


   tablespace_name


from


   dba_temp_files;


col tablespace_name for a30


select


   tablespace_name,


   contents


from


   dba_tablespaces


 where


    contents = 'temporary';


--Check if undo tablespace is online (if you are using automatic undo management)


select


 tablespace_name,contents


  from


 dba_tablespaces


 where


 contents = 'undo';


--Put all tablespace in read only mode (do not include temporary tablespace or tablespaces that has rollback segments)


select


   ?alter tablespace '||tablespace_name||' read only;'


from


   dba_tablespaces


where


   contents <> 'temporary'


and


   contents <> 'undo'


and


   tablespace_name not in ('SYSTEM','SYSAUX');




 


'ALTER TABLESPACE'||TABLESPACE_


-----------------------------------------------------------


alter tablespace  users read only;


alter tablespace  example read only;


alter tablespace  apps_ts_tx_data read only;


alter tablespace  pkg_data read only;


alter tablespace  pkg_idx read only;


alter tablespace  pkg_data_32M read only;


alter tablespace  pkg_idx_32M read only;


alter tablespace  pkg_data_32M_manual read only;


 


 


--Put the database in restricted mode


alter system enable restricted session;


 


System altered


 


col host_name for a20


select


   instance_name,


   host_name,


   logins


from


   v$instance;


 


INSTANCE_NAME    HOST_NAME            LOGINS


---------------- -------------------- ----------


ora11g           dbms.f2c.com.br      restricted


 


--Change the SYSTEM tablespace


exec dbms_space_admin.tablespace_migrate_to_local('SYSTEM');


 


 


 


--Verify the tablespace extent management


select


   tablespace_name,


   extent_management


from


   dba_tablespaces


where


   tablespace_name = 'SYSTEM';


 


TABLESPACE_NAME                EXTENT_MANAGEMENT


------------------------------ -----------------


SYSTEM                         local


 


--Disable restricted mode


alter system disable restricted session;


 


System altered


 


--Put tablespaces in reead write mode


select


   'alter  tablespace ' || tablespace_name || ' read write;'
from


   dba_tablespaces
where


   contents <> 'temporary'
and


   contents <> 'undo'
and


   tablespace_name not in ('SYSTEM', 'SYSAUX');


 


'ALTERTABLESPACE'||TABLESPACE_


------------------------------------------------------------


alter  tablespace users read write;


alter  tablespace example read write;


alter  tablespace apps_ts_tx_data read write;


alter  tablespace pkg_data read write;


alter  tablespace pkg_idx read write;


alter  tablespace pkg_data_32M read write;


alter  tablespace pkg_idx_32M read write;


alter  tablespace pkg_data_32M_manual read write;

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