Examine the following command used to perform incremental level 0 backup:
RMAN> BACKUP INCREMENTAL LEVEL 0 DATABASE;
To enable the block change tracking, after the incremental level 0 backup you issued the following
command:
SQL> ALTER DATABASE ENABLE BLOCK CHANGE TRACKING USING FILE ‘/mydir/
rman_change_track.f’;
To perform incremental level 1 cumulative backup, you issued the following command:
RMAN> BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE;
Which two statements are true in the above situation? (Choose two.)
A.
The block change tracking data will be used only from the next incremental 0 backup.
B.
The incremental backup will use change tracking data for accomplishing the backup.
C.
The incremental backup will not use change tracking data for accomplishing the backup.
D.
The block track file will scan all the blocks and create bitmap for all the blocks backed up in the
level 0
backup.
Explanation:
After enabling change tracking, the first level 0 incremental backup still has to scan the entire
datafile, as the change tracking file does not yet reflect the status of the blocks. Subsequent
incremental backup that use this level 0 as parent will take advantage of the change tracking file.
When some a chunk needs to be marked dirty for the first time after incremental backup, version
information in bitmap extent headers (X$KRCFBH) is initialized – XFLAGS is set to 2,
CURR_VERCNT and CURR_VERTIME
filled from datafile descriptor. If file had no changes since last incremental backup – nothing is
written to the bitmap. There is no difference in handling different backup levels. Version is created
in the same way whether its level 0, level 1 or level 4 backup. By the way, it seems that Oracle
10g documentation officially mentions only support for levels 0 and 1. However, I checked
incremental backup levels up to 4 and they do work (10.2.0.2).
Oracle Press 1Z0-053 Exam Guide, Chapter 4: Creating RMAN Backups
The first incremental level 0 backup reads every block in the datafile, and subsequent incremental
level 1 backups use the block change tracking file. No reference to create bitmap found.
http://download.oracle.com/docs/cd/B19306_01/backup.102/b14192/bkup004.htm#i1032148
RMAN’s change tracking feature for incremental backups improves incremental backup
performance by recording changed blocks in each datafile in a change tracking file. If change
tracking is enabled, RMAN uses the change tracking file to identify changed blocks for incremental
backup, thus avoiding the need to scan every block in the datafile. Using change tracking in no
way changes the commands used to pe form incremental backups, and the change tracking files
themselves generally require little maintenance after initial configuration.