問題：由于段延遲分配。導致新創建的表未分配段。與參數deferred_segment_creation有關。如果是空表，使用exp和imp會導致導不出來表結構。

使用exp加參數rows=n導出元數據，記錄一個問題
導入后，往表里插入數據，發現占用了很大的空間，經過排查是initial extent的問題。
使用rows=n,導出元數據，然后在導入到其它庫。initial extent會改變(新建立的表默認為64k)

怎樣才處理該問題？
ALTER TABLE <username>.<table_name> MOVE tablespace <tablespace_name> STORAGE(INITIAL 64k NEXT 1m);
ALTER INDEX <username>.<index_name> REBUILD online tablespace <tablespace_name> STORAGE(INITIAL 64k NEXT 1m);

測試：
1.查詢表的定義，initial默認為64k
SQL> select dbms_metadata.get_ddl('TABLE','T1','ERWA') from dual;

DBMS_METADATA.GET_DDL('TABLE','T1','ERWA')
--------------------------------------------------------------------------------

CREATE TABLE "ERWA"."T1"
( "EMPNO" NUMBER(4,0),
"ENAME" VARCHAR2(20),
"JOB" VARCHAR2(9),
"MGR" NUMBER(4,0),
"HIREDATE" DATE,
"SAL" NUMBER(7,2),
"COMM" NUMBER(7,2),
"DEPTNO" NUMBER(2,0)
) SEGMENT CREATION IMMEDIATE
PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255
NOCOMPRESS LOGGING
STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXT
ENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "USERS"

SQL>
2.使用rows=n導出
[oracle@lxtrac05 bk]$ exp system/oracle file=test.dmp tables=erwa.t1 rows=n
Export: Release 11.2.0.4.0 - Production on Thu Feb 22 11:14:16 2018
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP, Data Mining
and Real Application Testing options
Export done in UTF8 character set and AL16UTF16 NCHAR character set
server uses AL32UTF8 character set (possible charset conversion)
Note: table data (rows) will not be exported
About to export specified tables via Conventional Path ...
Current user changed to ERWA
. . exporting table T1
EXP-00091: Exporting questionable statistics.
Export terminated successfully with warnings.
[oracle@lxtrac05 bk]$
3.導入
[oracle@lxtrac05 bk]$ imp system/oracle file=test.dmp tables=t1 fromuser=erwa touser=srw
Import: Release 11.2.0.4.0 - Production on Thu Feb 22 11:15:27 2018
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP, Data Mining
and Real Application Testing options

Export file created by EXPORT:V11.02.00 via conventional path
import done in UTF8 character set and AL16UTF16 NCHAR character set
import server uses AL32UTF8 character set (possible charset conversion)
. importing ERWA's objects into SRW
Import terminated successfully without warnings.
[oracle@lxtrac05 bk]$
4.再次查詢表的定義結構。發現initial extent變了。
SQL> select dbms_metadata.get_ddl('TABLE','T1','SRW') from dual;
DBMS_METADATA.GET_DDL('TABLE','T1','SRW')
--------------------------------------------------------------------------------
CREATE TABLE "SRW"."T1"
( "EMPNO" NUMBER(4,0),
"ENAME" VARCHAR2(20),
"JOB" VARCHAR2(9),
"MGR" NUMBER(4,0),
"HIREDATE" DATE,
"SAL" NUMBER(7,2),
"COMM" NUMBER(7,2),
"DEPTNO" NUMBER(2,0)
) SEGMENT CREATION DEFERRED
PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255
NOCOMPRESS LOGGING
STORAGE( INITIAL 710934528 NEXT 1048576 MINEXTENTS 1
FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "USERS"

SQL>

?

轉載于:https://www.cnblogs.com/erwadba/p/8458634.html

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