Oracle11gr2新建空表不分配semgent



Oracle 11g r2的新特性，延迟段创建 ，就是说从11GR2开始默认创建的表不会立及分配segment，不会占用磁盘空间，这听上去也是很合

Oracle 11g r2的新特性，延迟段创建 ，就是说从11GR2开始默认创建的表不会立及分配segment，，不会占用磁盘空间，这听上去也是很合理的，当第一条数据insert时才会分配空间

试验一把

sys@ANBOB> conn anbob/anbob Connected. anbob@ANBOB> select * from v$version; BANNER -------------------------------------------------------------------------------- Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production PL/SQL Release 11.2.0.1.0 - Production CORE 11.2.0.1.0 Production TNS for Linux: Version 11.2.0.1.0 - Production NLSRTL Version 11.2.0.1.0 - Production anbob@ANBOB> create table testnew(id int primary key,name varchar2(10)); Table created. anbob@ANBOB> create table testnew_IME(id int primary key,name varchar2(10)) segment creation immediate; Table created. anbob@ANBOB> create table testnew_def(id int primary key,name varchar2(10)) segment creation deferred; Table created. anbob@ANBOB> select segment_name from user_segments where segment_name like 'TESTNEW%'; SEGMENT_NAME --------------------------------------------------------------------------------- TESTNEW_IME anbob@ANBOB> select INDEX_NAME,TABLE_OWNER from USER_indexes where table_name='TESTNEW'; INDEX_NAME TABLE_OWNER ------------------------------ ------------------------------ SYS_C0010903 ANBOB anbob@ANBOB> select INDEX_NAME,TABLE_OWNER from USER_indexes where table_name='TESTNEW_IME'; INDEX_NAME TABLE_OWNER ------------------------------ ------------------------------ SYS_C0010904 ANBOB anbob@ANBOB> select INDEX_NAME,TABLE_OWNER from USER_indexes where table_name='TESTNEW_DEF'; INDEX_NAME TABLE_OWNER ------------------------------ ------------------------------ SYS_C0010905 ANBOB anbob@ANBOB> select segment_name from user_segments where segment_name='SYS_C0010903'; no rows selected anbob@ANBOB> select segment_name from user_segments where segment_name='SYS_C0010904'; SEGMENT_NAME --------------------------------------------------------------------------------- SYS_C0010904 anbob@ANBOB> select segment_name from user_segments where segment_name='SYS_C0010905'; no rows selected anbob@ANBOB> insert into testnew values(1,'anbob.com'); 1 row created. anbob@ANBOB> commit; Commit complete. anbob@ANBOB> select segment_name from user_segments where segment_name like 'TESTNEW%'; SEGMENT_NAME --------------------------------------------------------------------------------- TESTNEW TESTNEW_IME anbob@ANBOB> select INDEX_NAME,TABLE_OWNER from USER_indexes where table_name='TESTNEW'; INDEX_NAME TABLE_OWNER ------------------------------ ------------------------------ SYS_C0010903 ANBOB anbob@ANBOB> select segment_name from user_segments where segment_name='SYS_C0010903'; SEGMENT_NAME --------------------------------------------------------------------------------- SYS_C0010903 anbob@ANBOB> truncate table testnew; Table truncated. anbob@ANBOB> select segment_name from user_segments where segment_name like 'TESTNEW%'; SEGMENT_NAME --------------------------------------------------------------------------------- TESTNEW TESTNEW_IME anbob@ANBOB> conn sys/oracle as sysdba Connected. sys@ANBOB> create table testnew_def(id int primary key,name varchar2(10)) segment creation deferred; create table testnew_def(id int primary key,name varchar2(10)) segment creation deferred * ERROR at line 1: ORA-14223: 此表不支持延迟创建段

note:
11g r2默认是使用segment creation deferred建立，新建的无记录表不分配sement,当insert 第一条记录时分配段空间，不会因truncate而回收，并且在sys schema里不支持,听说exp 也不会导出