=======================================================
Oracle: block change tracking
=======================================================
:Title:        Oracle: block change tracking
:Author:       Douglas O'Leary <dkoleary@olearycomputers.com>
:Description:  Oracle: block change tracking
:Date created: 07/27/2010
:Date updated: 07/27/2010
:Disclaimer:   Standard: Use the information that follows at your own risk.  If you screw up a system, don't blame it on me...

Block change tracking is used in conjunction with incremental backups. The 
block change tracking file, as you might imagine, is used to track the 
changes at the block level to each of the datafiles.

The block change tracking file size is automatically determined. It should 
be roughly 1/30,000 of the database size. The absolute minimum size is 320k 
per datafile so the file for my little database will be 5*320/1024 = 1.56 
megs. The file will hold enough data to support 8 days of incremental 
backups. Your base backup, then, has to be done minimally, once a week.

1.  To enable block change tracking::

        alter database enable block change tracking 
        using file '${absolute_path}' [ reuse ]

2.  To disable block change tracking::

        alter database disable block change tracking

3.  To identify status of block change tracking::

        SQL> select * from v$block_change_tracking;
        
        STATUS     FILENAME                                           BYTES
        ---------- --------------------------------------------- ----------
        DISABLED
        or
        SQL> select * from v$block_change_tracking;
        
        STATUS     FILENAME                                           BYTES
        ---------- --------------------------------------------- ----------
        ENABLED    /oracle/block_change/oci1_bc.fil                11599872