启用Block Change Tracking-10g新特性

Block chage tracking是Oracle10g的一个新特性，Block change tracking进程记录自从上一次备份以来数据块的变化，并把这些信息记录在跟踪文件中。RMAN使用这个文件判断增量备份中需要备份的变更数据。这极大的促进了备份性能，RMAN可以不再扫描整个文件以查找变更数据。

为此Oracle引入了一个新的后台进程，CTWR，其全称为Change Tracking Writer，用于记录变化的块并将变化写入相应的日志文件中。
启用跟踪可以使用如下命令:

alter database enable block change tracking using
file '/data5/flash_recovery_area/JAVIS/javis_block_track.log';

判断当前设置可以查询:

select filename,status,bytes from v$block_change_tracking;

关闭跟踪:

alter database disable block change tracking;

以下步骤供参考:

SYS AS SYSDBA on 29-MAR-05 >alter database enable block change tracking using
2  file '/data5/flash_recovery_area/JAVIS/javis_block_track.log';

Database altered.

SYS AS SYSDBA on 29-MAR-05 >select filename,status,bytes from v$block_change_tracking;

FILENAME
--------------------------------------------------------------------------------
STATUS          BYTES
---------- ----------
/data5/flash_recovery_area/JAVIS/javis_block_track.log
ENABLED      11599872

SYS AS SYSDBA on 29-MAR-05 >alter database disable block change tracking;

Database altered.

SYS AS SYSDBA on 29-MAR-05 >select filename,status,bytes from v$block_change_tracking;

FILENAME
--------------------------------------------------------------------------------
STATUS          BYTES
---------- ----------

DISABLED