question on rman backup incremental level 0
- From: Guang Mei <guangmei@xxxxxxxxx>
- To: oracle-l-freelists <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 27 Aug 2008 13:51:47 -0700 (PDT)
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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