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RE: Slick tricks for extent size reduction in LMTS via LMTS=>DM=> LMTS ?

From: Feighery Raymond <Raymond.Feighery_at_churchill.com>
Date: Wed, 21 Jul 2004 17:09:25 +0100
Message-ID: <817D2444710B934B9F7B8A1DAAF432D601F2AF5B@brcexm03> 





Version: 9.2.0.4


Platform: Solaris 8



Test Case:


Start out with uniform extent size of 20M and reduce to 1M






sys_at_ORCL9I.UK.X.CH> create tablespace lmt_test datafile
'/tmp/lmt_test_01.dmp' size 100m


  2  extent management local


  3  uniform size 20M;



Tablespace created.


sys_at_ORCL9I.UK.X.CH> select      tablespace_name,
  2                  initial_extent,
  3                  next_extent,
  4                  min_extlen,
  5                  extent_management,
  6                  allocation_type




  7  from dba_tablespaces where tablespace_name = 'LMT_TEST';


TABLESPACE_NAME                INITIAL_EXTENT NEXT_EXTENT MIN_EXTLEN


EXTENT_MAN ALLOCATIO



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



sys_at_ORCL9I.UK.X.CH> create table lmt_test_tab (col1 varchar2(10))
  2  tablespace lmt_test;



Table created.


sys_at_ORCL9I.UK.X.CH> select      segment_name,
  2                  bytes,
  3                  blocks,
  4                  extents,
  5                  initial_extent,
  6                  next_extent




  7  from dba_segments


  8  where segment_name = 'LMT_TEST_TAB';



SEGMENT_NAME         BYTES     BLOCKS    EXTENTS INITIAL_EXTENT NEXT_EXTENT



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

LMT_TEST_TAB      20971520       2560          1       20971520    20971520


sys_at_ORCL9I.UK.X.CH> exec


dbms_space_admin.tablespace_migrate_from_local('LMT_TEST');



PL/SQL procedure successfully completed.



sys_at_ORCL9I.UK.X.CH> alter table lmt_test_tab
  2  storage (next 1M);



Table altered.



sys_at_ORCL9I.UK.X.CH> alter tablespace lmt_test default storage (initial 1M
next 1M);



Tablespace altered.



sys_at_ORCL9I.UK.X.CH> alter tablespace lmt_test minimum extent 1M;



Tablespace altered.



sys_at_ORCL9I.UK.X.CH> exec


dbms_space_admin.tablespace_migrate_to_local('LMT_TEST',1);



PL/SQL procedure successfully completed.



sys_at_ORCL9I.UK.X.CH> alter table lmt_test_tab allocate extent;



Table altered.



sys_at_ORCL9I.UK.X.CH> create table lmt_test_tab2 (col1 varchar2(10))
tablespace lmt_test;



Table created.


sys_at_ORCL9I.UK.X.CH> select      tablespace_name,
  2                  initial_extent,
  3                  next_extent,
  4                  min_extlen,
  5                  extent_management,
  6                  allocation_type




  7  from dba_tablespaces where tablespace_name = 'LMT_TEST';


TABLESPACE_NAME                INITIAL_EXTENT NEXT_EXTENT MIN_EXTLEN


EXTENT_MAN ALLOCATIO



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




sys_at_ORCL9I.UK.X.CH> select      segment_name,
  2                  bytes,
  3                  blocks,
  4                  extents,
  5                  initial_extent,
  6                  next_extent




  7  from dba_segments


  8  where tablespace_name = 'LMT_TEST';



SEGMENT_NAME         BYTES     BLOCKS    EXTENTS INITIAL_EXTENT NEXT_EXTENT



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


LMT_TEST_TAB      22020096       2688          2       20971520     1048576
LMT_TEST_TAB2      1048576        128          1        1048576     1048576






-----Original Message-----



From: Mohan, Ross [mailto:RMohan_at_arbinet.com]
Sent: Wednesday, July 21, 2004 4:42 PM


To: oracle-l_at_freelists.org


Subject: RE: Slick tricks for extent size reduction in LMTS via
LMTS=>DM=> LMTS ?



Ray, 


Tried. Repeatedly. Gave me ora- error each time I tried to
shrink below the previous uniform size. "Invalid Size". 
No joy.



-----Original Message-----



From: Feighery Raymond [mailto:Raymond.Feighery_at_churchill.com] 
Sent: Wednesday, July 21, 2004 10:02 AM


To: 'oracle-l_at_freelists.org'


Subject: RE: Slick tricks for extent size reduction in LMTS via LMTS=>DM=>
LMTS ?



Ross



You can do it in the way your subject line suggests using:

1) dbms_space_admin.tablespace_migrate_from_local
2) alter tablespace (change default storage extent size and minimum extent)
3) dbms_space_admin.tablespace_migrate_to_local





However, already existing tables will retain their existing storage
parameters (unless you change them at step 2) and you will have to have a
dictionary managed SYSTEM tablespace to change the LMT to dictionary-managed
at step 1. 



dbms_space_admin.tablespace_migrate_to_local has some side effects. Although
you will get the performance benefits of an LMT you will no longer get the
policy enforcement of extent sizes (i.e. the ALLOCATION_TYPE column in
dba_tablespaces will show as USER not UNIFORM or SYSTEM). Another is that
the next extent storage attribute does not get reset on deallocation of
extents (this only matters if PCTINCREASE > 0).



Ray



-----Original Message-----



From: Mohan, Ross [mailto:RMohan_at_arbinet.com]
Sent: Wednesday, July 21, 2004 12:21 AM


To: oracle-l_at_freelists.org


Subject: Slick tricks for extent size reduction in LMTS via LMTS=>DM=>LMTS ?




I am gathering, painfully, that once you create and
partially populate a half terabyte tspace with local
ext mgmt extent size 100M there's no way to reduce
the extent size to, say, 5M. 


Please someone tell me I am wrong.






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Received on Wed Jul 21 2004 - 11:09:16 CDT












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