Block Change Tracking（块跟踪）详解

Block Change Tracking（块跟踪）主要用于RMAN备份的增量备份，记录自从上一次备份以来数据块的变化，相关后台进程CTWR（Change Tracking Writer）

改善增量备份性能，RMAN可以不再扫描整个文件以查找变更数据。从10g开始提供此功能。

le@vmrac1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.3.0 Production on Mon Oct 28 18:31:47 2013

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

 Connected to:
 Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
 With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,
 Data Mining and Real Application Testing options

SQL> -- 增量备份的数据块跟踪
SQL> select * from v$block_change_tracking;

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

SQL> -- 开启数据块跟踪功能
 SQL> alter database enable block change tracking;

Database altered.

SQL> select * from v$block_change_tracking;

STATUS     FILENAME                                                           BYTES
 ---------- --------------------------------------------------------------- ----------
 ENABLED    +DATA/rac/changetracking/ctf.279.830025153   11599872
            

SQL> -- 数据块跟踪进程CTWR
 SQL> host ps -ef | grep ctwr
 oracle   11886     1  0 18:32 ?        00:00:00 ora_ctwr_rac1
 oracle   11894 11875  0 18:32 pts/2    00:00:00 /bin/bash -c ps -ef | grep ctwr
 oracle   11896 11894  0 18:32 pts/2    00:00:00 grep ctwr

SQL> -- 关闭数据块更改跟踪功能
 SQL> alter database disable block change tracking;

Database altered.

SQL> select * from v$block_change_tracking;

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

SQL> -- 开启跟踪功能，并使用指定文件记录数据块更改
 SQL> alter database enable block change tracking using file '/home/oracle/ctf';

Database altered.

SQL> select * from v$block_change_tracking;

STATUS     FILENAME                          BYTES
 ---------- ------------------------------------ ----------
 ENABLED    /home/oracle/ctf               11599872

SQL> alter database disable block change tracking;

Database altered.

SQL> select * from v$block_change_tracking;

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

SQL> alter database enable block change tracking;

Database altered.
-- 自动生成跟踪文件

SQL> select * from v$block_change_tracking;

STATUS     FILENAME                                                            BYTES
 ---------- ----------------------------------------------------------------- ----------
 ENABLED    +DATA/rac/changetracking/ctf.280.830025283     11599872