OCP-1Z0-053-200题-33题-612

QUESTION 33

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.

Answer: AC

同612题：http://blog.csdn.net/rlhua/article/details/18823753

Explanation/Reference:

Section: Backup, Recovery & Recovery Manager (RMAN)

http://www.pythian.com/documents/Pythian-oracle-block-change.pdf

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 changetracking 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 backuplevels. 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 perform incremental backups, and the

change tracking files themselves generally require little maintenance after initial configuration.