I think Jonathan Lewis has explained the algorithm before, but it's also
something that we have investigated here.
The algorithm (ignoring some details) is:
There will be 4 extent sizes used, 64K, 1M, 8M, 64M
As long as object allocation is 1M or less, 64K extent sizes are used,
When object allocation is between 1M and 64M, 1M extent sizes are used.
When object allocation is between 64M and 1G, 8M extent sizes are used.
When object allocation is more than 1G, 64M extent sizes are used.
However, when you initially create the object, the extents are
determined by figuring out the space allocated to the newly created
object taking into account the INITIAL, NEXT, PCTINCREASE, MINEXTENTS
storage parameters. So the object might start off with 1M extents
instead of starting off with 64K extents. The algorithm is similar to
the one outlined above but it is more complicated. The NEXT and
PCTINCREASE seem to be ignored after the object is created.
e.g.
create table ... tablespace locally_managed_autoallocate
storage (initial 1M next 512K minextents 15 pctincrease 0) ...;
Initial allocation will be 1M + (15 - 1) * 512K = 8M
When you create the table, you will see eight extents, each of one
megabyte.
odshis_table_11.2.0.4.txt
---------------------------------------
(PARTITION "P_18991231" VALUES LESS THAN (TO_DATE(' 1899-12-31 00:00:00', 'SYYYY-MM-DD HH24:MI:SS'
, 'NLS_CALENDAR=GREGORIAN')) SEGMENT CREATION IMMEDIATE
PCTFREE 0 PCTUSED 40 INITRANS 1 MAXTRANS 255
NOCOMPRESS LOGGING <<<<<<<<<<<<<<<<<<<<<<<<<< NOCOMPRESS
STORAGE(INITIAL 8388608 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
ods_table_11.2.0.3.txt
---------------------------------------
...
(PARTITION "P_18991231" VALUES LESS THAN (TO_DATE(' 1899-12-31 00:00:00', 'SYY
YY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN')) SEGMENT CREATION DEFERRED
PCTFREE 0 PCTUSED 40 INITRANS 1 MAXTRANS 255
COMPRESS BASIC LOGGING <<<<<<<<<<<<<<<<<<<<<<<<< COMPRESS
########spool html format
-
SET markup html ON spool ON pre off entmap off
-
-
set term off
-
set heading on
-
set verify off
-
set feedback off
-
-
set linesize 2000
-
set pagesize 30000
-
set long 999999999
-
set longchunksize 999999
-
--------------------- 本文来自 suyishuai 的CSDN 博客 ，全文地址请点击：https://blog.csdn.net/suyishuai/article/details/22725543?utm_source=copy
######
------analyze_table_space script------
-----------------------------------------------------------------------------------------------------------<
set serveroutput on size 1000000
set feedback off
prompt Input segment name, owner (default current user), type (default table), partition name (default null)
DECLARE
p_segname varchar2(500);
p_owner varchar2(100);
p_type varchar2(100);
p_partition varchar2(500);
l_free_blks number;
l_total_blocks number;
l_total_bytes number;
l_unused_blocks number;
l_unused_bytes number;
l_lastUsedExtFileId number;
l_lastUsedExtBlockId number;
l_last_used_block number;
l_segment_space_mgmt varchar2(255);
l_unformatted_blocks number;
l_unformatted_bytes number;
l_fs1_blocks number;
l_fs1_bytes number;
l_fs2_blocks number;
l_fs2_bytes number;
l_fs3_blocks number;
l_fs3_bytes number;
l_fs4_blocks number;
l_fs4_bytes number;
l_full_blocks number;
l_full_bytes number;
procedure p(p_label in varchar2,p_num in number)
as
begin
dbms_output.put_line(rpad(p_label,40,'.')||to_char(p_num,'999,999,999,999'));
end;
begin
p_segname := upper('&p_segname');
p_owner := upper('&p_owner');
if p_owner is null then
p_owner := user;
end if;
p_type := upper('&p_type');
if p_type is null then
p_type := 'TABLE';
end if;
p_partition := upper('&p_partition');
begin
execute immediate 'select ts.segment_space_management
from dba_segments seg,dba_tablespaces ts
where seg.segment_name=:p_segname
and (:p_partition is null or seg.partition_name =:p_segname)
and seg.owner=:p_owner
and seg.tablespace_name=ts.tablespace_name'
into l_segment_space_mgmt
using p_segname,p_partition,p_partition,p_owner;
exception
when too_many_rows then
dbms_output.put_line('This must be a partitioned table,use p_partition=>');
return;
end;
if l_segment_space_mgmt='AUTO'
then
dbms_space.space_usage(p_owner,p_segname,p_type,
l_unformatted_blocks,
l_unformatted_bytes,
l_fs1_blocks,l_fs1_bytes,
l_fs2_blocks,l_fs2_bytes,
l_fs3_blocks,l_fs3_bytes,
l_fs4_blocks,l_fs4_bytes,
l_full_blocks,l_full_bytes,p_partition);
p('Unformatted Block ',l_unformatted_blocks);
p('FS1 Blocks (0-25) ',l_fs1_blocks);
p('FS2 Blocks (25-50) ',l_fs2_blocks);
p('FS3 Blocks (50-75) ',l_fs3_blocks);
p('FS4 Blocks (75-100) ',l_fs4_blocks);
p('Full Blocks ',l_full_blocks);
else
dbms_space.free_blocks(segment_owner=>p_owner,
segment_name=>p_segname,
segment_type=>p_type,
freelist_group_id=>0,
free_blks=>l_free_blks);
p('Free Blocks',l_free_blks);
end if;
dbms_space.unused_space(segment_owner=>p_owner,
segment_name=>p_segname,
segment_type=>p_type,
total_blocks=>l_total_blocks,
total_bytes=>l_total_bytes,
unused_blocks=>l_unused_blocks,
unused_bytes=>l_unused_bytes,
last_used_extent_file_id=>l_lastUsedExtFileId,
last_used_extent_block_id=>l_lastUsedExtBlockId,
last_used_block=>l_last_used_block,
partition_name=>p_partition);
p('Total Blocks',l_total_blocks);
p('Total Bytes',l_total_bytes);
p('Total MBytes',trunc(l_total_bytes/1024/1024));
p('Unused Blocks',l_unused_blocks);
p('Unused Bytes',l_unused_bytes);
p('Last Used Ext FileId',l_lastUsedExtFileId);
p('Last Used Ext BlockId',l_lastUsedExtBlockId);
p('Last Used Block',l_last_used_block);
END; -- Procedure
/
example:
nput segment name, owner (default current user), type (default table), partition name (default null)
Enter value for p_segname: BAK1604_E002_SYM_RB_ACCT
old 35: p_segname := upper('&p_segname');
new 35: p_segname := upper('BAK1604_E002_SYM_RB_ACCT');
Enter value for p_owner: OMLOPR
old 37: p_owner := upper('&p_owner');
new 37: p_owner := upper('OMLOPR');
Enter value for p_type: TABLE PARTITION
old 42: p_type := upper('&p_type');
new 42: p_type := upper('TABLE PARTITION');
Enter value for p_partition: P_29991231
###solution:
方法1：
the way to compress data after it is inserted via a non-direct operation is to move the table and compress the data:
alter table compressed move compress;方法2：DataPump utilities (expdp/impdp) perform direct path operations and so the table compression is maintained
impdp test/test directory=dpu dumpfile=test_compress.dmp tables=compressed,noncompressed
参考方法：
ps: 数据压缩相关技术点
哪些表是压缩表？
欲查询哪些表进行了压缩，可查询如下视图：
SQL> SELECT table_name, compression, compress_for FROM user_tables; TABLE_NAME COMPRESSION COMPRESS_FOR ---------------- ------------ ----------------- T1 DISABLED T2 ENABLED BASIC T3 ENABLED OLTP T4 ENABLED QUERY HIGH T5 ENABLED ARCHIVE LOW
欲查询哪些分区表进行了压缩，可查询如下视图：
SQL> SELECT table_name, partition_name, compression, compress_for FROM user_tab_partitions; TABLE_NAME PARTITION_NAME COMPRESSION COMPRESS_FOR ----------- ---------------- ----------- ---------------SALES Q4_2004 ENABLED ARCHIVE HIGH SALES Q3_2008 ENABLED QUERY HIGH SALES Q4_2008 ENABLED QUERY HIGH SALES Q1_2009 ENABLED OLTP SALES Q2_2009 ENABLED OLTP ...
如何更改压缩算法？
一个表的压缩算法是可以更改的，从而适应于不同数据变化情况。例如，交易明细当前数据可采取OLTP压缩算法，而针对超过6个月极少更改的数据可采取Warehouse压缩算法。
以下语句将表转换为basic压缩表：
SQL> alter table emp move compress basic;
以下语句将表转换为OLTP压缩表：
SQL> alter table emp move compress for oltp;
以下语句一个分区转换为basic压缩分区:
SQL>alter table part_objects move partition p3 compress basic;
以下语句修改一个分区的现有压缩算法，但更改之后的压缩算法只对新记录有效，而不影响现有记录。
SQL>alter table part_objects modify partition p1 compress for oltp;
上述move和modify操作均非在线操作，即在进行这些操作时，这些表将不可进行DML操作。欲在线进行压缩算法变更操作，则需要采用表在线重定义技术。限于篇幅，不赘述。请参考Oracle相关联机文档。
哪些记录是压缩记录？
由于表的压缩算法可更改，这样一个表中的记录可以是非压缩或采取不同压缩算法的。欲查询不同记录的压缩情况，可通过记录的ROWID值进行如下查询：
SELECT DECODE(DBMS_COMPRESSION.GET_COMPRESSION_TYPE( ownname => 'HR', tabname => 'EMPLOYEES', row_id => 'AAAVEIAAGAAAABTAAD'), 1, 'No Compression', 2, 'Basic or OLTP Compression', 4, 'Hybrid Columnar Compression for Query High', 8, 'Hybrid Columnar Compression for Query Low', 16, 'Hybrid Columnar Compression for Archive High', 32, 'Hybrid Columnar Compression for Archive Low', 'Unknown Compression Type') compression_type FROM DUAL;
其它技术点
- 压缩表不支持在线shrink操作。
- 表压缩技术不适合于11g新的大对象技术：SecureFiles。因为SecureFiles采用自己的压缩技术。
- 当表采用basic压缩算法之后，表的PCTFREE参数自动设置为0。
- 使用COMPRESS FOR OLTP 或COMPRESS BASIC方式表的字段数量不能超过255个。虽然可以设置成功，但数据实际上是没有压缩的。
- IOT表不支持压缩。
######### for table and owner sgent and extent size
set pause off
prompt
/* Create an SQLPLUS variable, containing the block size */
col res new_value block_size noprint
select value res
from v$parameter
where name = 'db_block_size';
accept ownr char prompt 'Give owner to display extents of: '
accept oname char prompt 'Give table name to display extents of: '
set verify off
set feed off
col tn format a10 heading 'Name' trunc
col init format 9,999,999 heading 'Init'
col next format 9,999,999 heading 'Next'
col mi format 999 heading 'Min'
col ma format 9999999999 heading 'Max'
col pct format 990 heading 'PctInc'
col s_init format a12 heading 'Init'
col s_next format a12 heading 'Nxt to alloc'
col sn format a15 heading 'Segment Name'
col tn format a15 heading 'Tabspace/FileID'
col st format a10 heading 'Type'
col bytes format 999,999,999
break on report
compute sum of bytes blocks on report
clear screen
prompt Storage params for the tablespace the object is in:
select distinct
d.tablespace_name tn,
initial_extent / &block_size || ' (' || initial_extent || ')' s_init,
next_extent / &block_size || ' (' || next_extent || ')' s_next,
pct_increase pct,
min_extents mi,
max_extents ma
from sys.dba_tablespaces d, sys.dba_extents u
where u.segment_name = upper('&oname')
and d.tablespace_name = u.tablespace_name
and u.owner = upper('&ownr');
prompt
prompt Storage params for the segment the object is in:
select distinct
s.segment_name sn,
t.initial_extent||' ('||t.initial_extent / &block_size||')' s_init,
t.next_extent||' ('||t.next_extent / &block_size||')' s_next,
t.pct_increase pct,
t.min_extents mi,
t.max_extents ma
from sys.dba_segments s, sys.dba_tables t
where s.segment_name = upper('&oname')
and s.owner = upper('&ownr')
and t.owner = upper('&ownr')
and t.table_name = s.segment_name(+);
prompt
prompt Overview of all the allocated extents in this segment:
col st format a8
col bts format 999999999999999999999 heading "Bytes"
col bks format 9999 heading "Blocks"
col bi format 9999999999999999999 heading "1st Blck"
select extent_id, segment_name sn, segment_type st,
tablespace_name||'/'||file_id tn,
bytes bts, blocks bks, block_id bi
from sys.dba_extents
where segment_name = upper('&oname')
and owner = upper('&ownr')
order by bytes,extent_id;
pause Return...
clear screen
set pause on
set pause Return...
col owner format a15
prompt Overview of all extents in same tablespace ordered by size
select segment_name sn, segment_type st, extent_id, owner, bytes, blocks
from sys.dba_extents
where tablespace_name = (select tablespace_name from sys.dba_segments
where segment_name = upper('&oname')
and owner = upper('&ownr') )
order by bytes desc;
set verify on
set feed on
clear columns
clear breaks
clear computes
/
example:
nput segment name, owner (default current user), type (default table), partition name (default null)
Enter value for p_segname: BAK1604_E002_SYM_RB_ACCT
old 35: p_segname := upper('&p_segname');
new 35: p_segname := upper('BAK1604_E002_SYM_RB_ACCT');
Enter value for p_owner: OMLOPR
old 37: p_owner := upper('&p_owner');
new 37: p_owner := upper('OMLOPR');
Enter value for p_type: TABLE PARTITION
old 42: p_type := upper('&p_type');
new 42: p_type := upper('TABLE PARTITION');
Enter value for p_partition: P_29991231
###########v0 for user all table avg size
drop table column_counts;
create table column_counts
(
table_name,
column_count
)
as
(
select table_name, max(column_id)
from user_tab_columns
where data_type not like 'LONG%' AND table_name in
(select table_name from user_tables)
group by table_name
)
;
set pages 0
set tab on
set trim on
set verify off
set feedback off
set termout off
set head off
set lines 100
set recsep off
set embedded on
spool getavgcol.sql
prompt column TB format A30
prompt set head off recsep off
prompt set lines 80 feedback off pages 0
prompt spool getavgcol
REM
column select_line format A8
column end_line format A1
column from_stmt format A34 word_wrap
column col_nm format A100
column col_val format A32
column tnm1 noprint
column tnmprint format A37
column column_id noprint
break on tnm1 skip 2
set null ''
clear breaks
select UTC.table_name tnm1,
decode(column_id,1,'select ' || chr(39) || UTC.table_name || chr(39) ||
' TB, ', ' ') ||
'round(avg(nvl(vsize('||column_name||'),0)),0)' ||
decode(column_id,column_count, ' row_size from ' || UTC.table_name
|| ';'|| chr(10)||chr(10),
' +') col_nm
from user_tab_columns UTC, column_counts CC
where UTC.data_type not like 'LONG%' AND UTC.table_name = CC.table_name
order by UTC.table_name, UTC.column_id;
prompt spool off
prompt exit
spool off
drop table column_counts;
exit
##########v1 for tbale avg size
drop table column_counts;
create table column_counts
(
table_name,
column_count
)
as
(
select upper('&oname'), max(column_id)
from dba_tab_columns
where data_type not like 'LONG%' AND
table_name = upper('&oname')
);
set pages 0
set tab on
set trim on
set verify off
set feedback off
set termout off
set head off
set lines 100
set recsep off
set embedded on
spool getavgcol.sql
prompt column TB format A30
prompt set head off recsep off
prompt set lines 80 feedback off pages 0
prompt spool getavgcol
REM
column select_line format A8
column end_line format A1
column from_stmt format A34 word_wrap
column col_nm format A100
column col_val format A32
column tnm1 noprint
column tnmprint format A37
column column_id noprint
break on tnm1 skip 2
set null ''
clear breaks
select UTC.table_name tnm1,
decode(column_id,1,'select ' || chr(39) || UTC.table_name || chr(39) ||
' TB, ', ' ') ||
'round(avg(nvl(vsize('||column_name||'),0)),0)' ||
decode(column_id,column_count, ' row_size from ' || UTC.owner || '.'||UTC.table_name
|| ';'|| chr(10)||chr(10),
' +') col_nm
from dba_tab_columns UTC, column_counts CC
where UTC.data_type not like 'LONG%' AND UTC.table_name = CC.table_name
order by UTC.table_name, UTC.column_id;
prompt spool off
prompt exit
spool off
drop table column_counts;
exit