Oracle DBA_EXTENTS视图与 DBA_SEGMENTS视图

浏览数：23 / 时间：2015年06月12日

DBA_EXTENTS describes the extents comprising the segments in all tablespaces in the database.

Note that if a datafile (or entire tablespace) is offline in a locally managed tablespace, you will not see any extent information. If an object has extents in an online file of the tablespace, you will see extent information about the offline datafile. However, if the object is entirely in the offline file, a query of this view will not return any records.

Related View

USER_EXTENTS describes the extents comprising the segments owned by the current user‘s objects. This view does not display the OWNER, FILE_ID, BLOCK_ID, or RELATIVE_FNO columns.

也就是说DBA_EXTENDS描述的是数据库所有表空间中段的扩展信息。使用DBA_EXTENDS必须保证相应的数据文件处于online状态，否则无法返回任何记录。对于一用于，常使用的是USER_EXTENTS视图，比DBA_EXTENDS视图少几个字段。

--------------------------------------------------------------------------------------------------------------------------------

DBA_SEGMENTS describes the storage allocated for all segments in the database.

Related View

USER_SEGMENTS describes the storage allocated for the segments owned by the current user‘s objects. This view does not display the OWNER, HEADER_FILE, HEADER_BLOCK, or RELATIVE_FNO columns.

DBA_SEGMENTS 视图描述的是数据库中所有段的存储和分配信息。