question on rman backup incremental level 0

From: Guang Mei <guangmei_at_yahoo.com>
Date: Wed, 27 Aug 2008 13:51:47 -0700 (PDT)
Message-ID: <585832.69484.qm@web39507.mail.mud.yahoo.com>

Windows: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0

when I ran this on a very simple db:

RMAN> spool log to c:\temp\rman_test_log.txt RMAN> run {

2> allocate channel dev1 type disk;
3> backup incremental level 0
4> format 'c:\temp\level0_%U'
5> database;
6> release channel dev1;
7> }

RMAN> spool log off;

I got something like:

---

RMAN> 2> 3> 4> 5> 6> 7>
using target database control file instead of recovery catalog allocated channel: dev1
channel dev1: sid=78 devtype=DISK

Starting backup at 27-AUG-08
channel dev1: starting incremental level 0 datafile backupset channel dev1: specifying datafile(s) in backupset

input datafile fno=00001 name=C:\ORACLE\PRODUCT\10.2.0\ORADATA\GMTEST\SYSTEM01.DBF
input datafile fno=00003 name=C:\ORACLE\PRODUCT\10.2.0\ORADATA\GMTEST\SYSAUX01.DBF
input datafile fno=00002 name=C:\ORACLE\PRODUCT\10.2.0\ORADATA\GMTEST\UNDOTBS01.DBF
input datafile fno=00004 name=C:\ORACLE\PRODUCT\10.2.0\ORADATA\GMTEST\USERS01.DBF

channel dev1: starting piece 1 at 27-AUG-08 channel dev1: finished piece 1 at 27-AUG-08 piece handle=C:\TEMP\LEVEL0_0GJP3GH1_1_1 tag=TAG20080827T143720 comment=NONE

channel dev1: backup set complete, elapsed time: 00:00:45
channel dev1: starting incremental level 0 datafile backupset
channel dev1: specifying datafile(s) in backupset

including current control file in backupset including current SPFILE in backupset
channel dev1: starting piece 1 at 27-AUG-08 channel dev1: finished piece 1 at 27-AUG-08 piece handle=C:\TEMP\LEVEL0_0HJP3GIE_1_1 tag=TAG20080827T143720 comment=NONE channel dev1: backup set complete, elapsed time: 00:00:03 Finished backup at 27-AUG-08

released channel: dev1

---

Two questions:

1. If I compare the size of oracle data files (summed) and file "LEVEL0_0GJP3GH1_1_1". The "LEVEL0_0GJP3GH1_1_1" is smaller. Is this because RMAN level 0 backup only backs up the blocks that have been written, and escapes empty blocks in data files?
2. How does RMAN determine which datafiles to group together, to create different backupsets? If I have a db with many tablespaces and many data files, how does oracle decide which data file goes to which backupset? I found that datafiles from different tablespaces are grouped together (randomly?) to create different backupsets.

Thanks.
Guang       

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Received on Wed Aug 27 2008 - 15:51:47 CDT