怎么获得datafile备份的 增长信息?

来源于：
HOWTO get information about the growth of the datafile backup (文档 ID 352777.1)

适用于：
Oracle Server - Enterprise Edition - Version: 8.1.7.4 to 10.2.0.1 - Release: 8.1.7 to 10.2
Oracle Server - Enterprise Edition - Version: 8.1.7.4 to 11.1.0.7 [Release: 8.1.7 to 11.1]
Information in this document applies to any platform.

目标：
在如下的情况下是很有用的：
--备份时间增加的检查时
--未来的备份空间需求
--Filling grade of a datafile.

解决方案：
可以从RC_BACKUP_DATAFILE 或者 V$BACKUP_DATAFILE中去查询。

BLOCKS 列是被backed up 的block的数量(即：参与备份的block的数量)
DATAFILE_BLOCKS 列是 该datafile中总共的block的数量。

MAN catalog :
Example for the increase in the last 14 days :

SQL> select file#, min(blocks), max(blocks), max(blocks) - min(blocks)
     from rc_backup_datafile
     where db_name='V920'
     and completion_time > sysdate - 14
     group by file#
     order by max(blocks)- min(blocks);

controlfile:
SQL> select file#, min(blocks), max(blocks), max(blocks) - min(blocks)
     from v$backup_datafile
     where completion_time > sysdate - 14
     group by file#
     order by max(blocks)- min(blocks);