The SET DEFAULT...TABLESPACE clause of the CREATE DATABASE statement to
determines the default type of tablespace for this database in subsequent CREATE
TABLESPACE statements. Specify either SET DEFAULT BIGFILE TABLESPACE or
SET DEFAULT SMALLFILE TABLESPACE. If you omit this clause, the default is a
smallfile tablespace, which is the traditional type of Oracle Database tablespace. A
smallfile tablespace can contain up to 1022 files with up to 4M blocks each.

The use of bigfile tablespaces further enhances the Oracle-managed files feature,
because bigfile tablespaces make datafiles completely transparent for users. SQL
syntax for the ALTER TABLESPACE statement has been extended to allow you to
perform operations on tablespaces, rather than the underlying datafiles.

To dynamically change the default tablespace type after database creation, use the SET
DEFAULT TABLESPACE clause of the ALTER DATABASE statement:

ALTER DATABASE SET DEFAULT BIGFILE TABLESPACE;

You can determine the current default tablespace type for the database by querying the
DATABASE_PROPERTIES data dictionary view as follows:

SELECT PROPERTY_VALUE FROM DATABASE_PROPERTIES
WHERE PROPERTY_NAME = 'DEFAULT_TBS_TYPE';

指定默认的表空间文件类型
1. 可利用 set defaukt tablespace 来指定默认的表空间文件类型
2. 大文件表空间增强了OMF特性 , 使数据文件完全透明于用户
3. 数据库创建后 ,可利用 ALTER DATABASE SET DEFAULT BIGFILE TABLESPACE;
来改变默认的表空间文件类型
4. 通过SELECT PROPERTY_VALUE FROM DATABASE_PROPERTIES
WHERE PROPERTY_NAME = 'DEFAULT_TBS_TYPE';
可查询当前默认的表空间文件类型