RMAN and Begin backup mode

Question

Hi guys I have a couple of questiopns...
I want to know whether data is written to datafiles by DBWR when the datafile is in begin backup mode.
What is the difference in archive log creation during normal operation of a database and operation of a database during RMAN backup?

Answer 1

user13087302 wrote:
Normally, Oracle should write only changes into redolog files. But if tablespace is in backup mode, then entire block will be put into redolog as soon as this change it is 1st change occured on that block after enabling backup mode. That is why, we face massive redo log generation if the tablespace is in backup mode. So, logically you should be able to recover to the last SCN you have in hands.What do you mean by last SCN.Is it the SCN before puttting the tablespace in backup mode?Does that mean data present in other files will also be lost even though they are written in datafiles..Pls, look:
SQL> create tablespace myts1 datafile 'C:\app\oracle\oradata\testdb\myts1.dbf' size 10m;
Tablespace created.
SQL> create tablespace myts2 datafile 'C:\app\oracle\oradata\testdb\myts2.dbf' size 10m;
Tablespace created.
SQL> create table myt1 tablespace myts1 as select * from dba_objects where rownum<10001;
Table created.
SQL> create table myt2 tablespace myts2 as select * from dba_objects where rownum<10001;
Table created.
SQL> alter tablespace myts1 begin backup;
Tablespace altered.
SQL> create table myt1_1 tablespace myts1 as select * from dba_objects where rownum<10001;
Table created.
SQL> create table myt2_1 tablespace myts2 as select * from dba_objects where rownum<10001;
Table created.
SQL> create table myt1_3 tablespace myts1 as select * from dba_objects where rownum<10001;
Table created.Backup database:
C:\Documents and Settings\Administrator>rman target /
Recovery Manager: Release 11.2.0.1.0 - Production on Wed Nov 3 15:46:55 2010
Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.
connected to target database: TESTDB (DBID=2517263760)
RMAN> backup database;
Starting backup at 03-NOV-10
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=44 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00001 name=C:\APP\ORACLE\ORADATA\TESTDB\SYSTEM01.DBF
input datafile file number=00002 name=C:\APP\ORACLE\ORADATA\TESTDB\SYSAUX01.DBF
input datafile file number=00003 name=C:\APP\ORACLE\ORADATA\TESTDB\UNDOTBS01.DBF
input datafile file number=00005 name=C:\APP\ORACLE\ORADATA\TESTDB\EXAMPLE01.DBF
input datafile file number=00006 name=C:\APP\ORACLE\ORADATA\TESTDB\MYTS1.DBF
input datafile file number=00007 name=C:\APP\ORACLE\ORADATA\TESTDB\MYTS2.DBF
input datafile file number=00004 name=C:\APP\ORACLE\ORADATA\TESTDB\USERS01.DBF
channel ORA_DISK_1: starting piece 1 at 03-NOV-10
channel ORA_DISK_1: finished piece 1 at 03-NOV-10
piece handle=C:\APP\ORACLE\FLASH_RECOVERY_AREA\PRIM_DB\BACKUPSET\2010_11_03\O1_MF_NNNDF_TAG20101103T154701_6F2LXQ5C_.BKP tag=TAG20101103T154701 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:01:35
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
including current control file in backup set
including current SPFILE in backup set
channel ORA_DISK_1: starting piece 1 at 03-NOV-10
channel ORA_DISK_1: finished piece 1 at 03-NOV-10
piece handle=C:\APP\ORACLE\FLASH_RECOVERY_AREA\PRIM_DB\BACKUPSET\2010_11_03\O1_MF_NCSNF_TAG20101103T154701_6F2M0PJ3_.BKP tag=TAG20101103T154701 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 03-NOV-10
Recovery Manager complete.
SQL> select current_scn from v$database;
CURRENT_SCN
    1466019
SQL> drop table myt1_3 purge;
Table dropped.So, we dropped table MYT1_3 and now trying incomplete recovery.
SQL> shutdown abort;
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
Total System Global Area  431038464 bytes
Fixed Size                  1375088 bytes
Variable Size             322962576 bytes
Database Buffers          100663296 bytes
Redo Buffers                6037504 bytes
Database mounted. C:\Documents and Settings\Administrator>rman target /
Recovery Manager: Release 11.2.0.1.0 - Production on Wed Nov 3 15:51:51 2010
Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.
connected to target database: TESTDB (DBID=2517263760, not open)
RMAN> run
2> {
3> set until scn 1466019;
4> restore database;
5> recover database;
6> sql 'alter database open resetlogs';
7> }
executing command: SET until clause
Starting restore at 03-NOV-10
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=20 device type=DISK
channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00001 to C:\APP\ORACLE\ORADATA\TESTDB\SYS
TEM01.DBF
channel ORA_DISK_1: restoring datafile 00002 to C:\APP\ORACLE\ORADATA\TESTDB\SYSAUX01.DBF
channel ORA_DISK_1: restoring datafile 00003 to C:\APP\ORACLE\ORADATA\TESTDB\UNDOTBS01.DBF
channel ORA_DISK_1: restoring datafile 00004 to C:\APP\ORACLE\ORADATA\TESTDB\USERS01.DBF
channel ORA_DISK_1: restoring datafile 00005 to C:\APP\ORACLE\ORADATA\TESTDB\EXAMPLE01.DBF
channel ORA_DISK_1: restoring datafile 00006 to C:\APP\ORACLE\ORADATA\TESTDB\MYTS1.DBF
channel ORA_DISK_1: restoring datafile 00007 to C:\APP\ORACLE\ORADATA\TESTDB\MYTS2.DBF
channel ORA_DISK_1: reading from backup piece C:\APP\ORACLE\FLASH_RECOVERY_AREA\
PRIM_DB\BACKUPSET\2010_11_03\O1_MF_NNNDF_TAG20101103T154701_6F2LXQ5C_.BKP
channel ORA_DISK_1: piece handle=C:\APP\ORACLE\FLASH_RECOVERY_AREA\PRIM_DB\BACKUPSET\2010_11_03\O1_MF_NNNDF_TAG20101103T154701_6F2LXQ5C_.BKP tag=TAG20101103T154701
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:01:45
Finished restore at 03-NOV-10
Starting recover at 03-NOV-10
using channel ORA_DISK_1
starting media recovery
media recovery complete, elapsed time: 00:00:03
Finished recover at 03-NOV-10
sql statement: alter database open resetlogs
RMAN>Now, check tables:
SQL> select count(*) from myt1;
  COUNT(*)
     10000
SQL> select count(*) from myt2;
   COUNT(*)
     10000
SQL> select count(*) from myt1_3;
  COUNT(*)
     10000
SQL> select count(*) from myt2_1;
  COUNT(*)
     10000So, it does not matter what is the status of any tablespace: in backup mode or not. Incomplete recovery uses archivelogs + redologs.