DEFERRED_SEGMENT_CREATION

Property	Description
Parameter type	Boolean
Default value	true
Modifiable	ALTER SESSION, ALTER SYSTEM
Range of values	true \| false
Basic	No

DEFERRED_SEGMENT_CREATION specifies the semantics of deferred segment creation. If set to true, then segments for tables and their dependent objects (LOBs, indexes) will not be created until the first row is inserted into the table.

Before creating a set of tables, if it is known that a significant number of them will not be populated, then consider setting this parameter to true. This saves disk space and minimizes install time.

另外,ORACLE 11G在用EXPORT导出时，没有分配segment的空表将不能导出。

如果想在创建表的时候,同时创建段可以使用如下语法:

create table test(id number(10)) SEGMENT CREATION IMMEDIATE;

select table_name,segment_created from user_tables;

TABLE_NAME                     SEG
------------------------------          ---
TEST                                      YES

如果要在创建的时候不创建段可以使用如下语法(非sys用户):

create table test(id number(10)) SEGMENT CREATION DEFFERRD;

如果想将没有分配segment的空表导出来可以使用expdp.

ITPub博客

11GR2新特性(DEFERRED_SEGMENT_CREATION)

DEFERRED_SEGMENT_CREATION

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