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Note: The article ( named
Testing Media Block Recovery (MBR) using RMAN
) was taken from
www.in-oracle.com.
1.
Test that there are no data block corruption in scott.EMP table
alter
system flush buffer_cache; force to get the data from the data
file and not from the buffer cache.
2.
Generate a data block corruption for EMP table
>> Find a block which keep EMP data :
SQL> col HEADER_BLOCK format 99999999
SQL> col SEGMENT_NAME format a12
SQL> col NAME format a35
SQL>
select d.name, s.header_block, s.segment_name
from dba_segments s,
v$datafile_header d
where s.TABLESPACE_NAME = d.TABLESPACE_NAME
and s.segment_name = 'EMP'
and owner='SCOTT';
>> Write something wrong to the block 28 (the next block
after the header) to corrupt the block (at the OS level):
$ dd if=/dev/zero of=/DB1/oradata/db1/users01.dbf bs=8192 conv=notrunc seek=28 count=1
bs = block size
conv = convert the file ( In this case = do not truncate
the output file)
seek = which block will be corrupt
count = how many blocks
>> Verify the data block corruption:
SQL> select * from emp;
select * from emp
*
ERROR at line 1:
ORA-08103: object no longer exists
NOTE:
Select count(*) from emp; could be used also if there are no
indexes on the emp table;
3.
Recover the corrupted block with RMAN
RMAN>
blockrecover datafile 4 block 28;
Starting blockrecover at 03-FEB-08
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=144 devtype=DISK
channel ORA_DISK_1: restoring block(s)
channel ORA_DISK_1: specifying block(s) to restore from backup set
restoring blocks of datafile 00004
channel ORA_DISK_1: reading from backup piece /home/oracle/Desktop/Backup_rman/b ackup/bk_34_1_645659824
channel ORA_DISK_1: restored block(s) from backup piece 1
piece handle=/home/oracle/Desktop/Backup_rman/backup/bk_34_1_645659824 tag=HOT_D B_BK_LEVEL0
channel ORA_DISK_1: block restore complete, elapsed time: 00:00:01
starting media recovery
archive log thread 1 sequence 3 is already on disk as file /DB1/flash_recovery_a rea/DB1/archivelog/2008_02_02/o1_mf_1_3_3tb95vdp_.arc
archive log thread 1 sequence 4 is already on disk as file /DB1/flash_recovery_a rea/DB1/archivelog/2008_02_02/o1_mf_1_4_3tbbkzk3_.arc
channel ORA_DISK_1: starting archive log restore to default destination
channel ORA_DISK_1: restoring archive log
archive log thread=1 sequence=1
channel ORA_DISK_1: reading from backup piece /home/oracle/Desktop/Backup_rman/b ackup/al_38_1_645659875
channel ORA_DISK_1: restored backup piece 1
piece handle=/home/oracle/Desktop/Backup_rman/backup/al_38_1_645659875 tag=TAG20 080202T215755
channel ORA_DISK_1: restore complete, elapsed time: 00:00:01
channel ORA_DISK_1: deleting archive log(s)
archive log filename=/DB1/flash_recovery_area/DB1/archivelog/2008_02_03/o1_mf_1_ 1_3tbj3q9x_.arc recid=21 stamp=645668279
channel ORA_DISK_1: starting archive log restore to default destination
channel ORA_DISK_1: restoring archive log
archive log thread=1 sequence=2
channel ORA_DISK_1: reading from backup piece /home/oracle/Desktop/Backup_rman/b ackup/al_40_1_645659877
channel ORA_DISK_1: restored backup piece 1
piece handle=/home/oracle/Desktop/Backup_rman/backup/al_40_1_645659877 tag=TAG20 080202T215755
channel ORA_DISK_1: restore complete, elapsed time: 00:00:01
channel ORA_DISK_1: deleting archive log(s)
archive log filename=/DB1/flash_recovery_area/DB1/archivelog/2008_02_03/o1_mf_1_ 2_3tbj3skx_.arc recid=22 stamp=645668281
media recovery complete, elapsed time: 00:00:01
Finished blockrecover at 03-FEB-08
4.
Test that there are no data block corruption in scott.EMP table
select EMPNO,ENAME,JOB,MGR, HIREDATE from emp;
will returm the emp data:
Note: The article ( named
Testing Media Block Recovery (MBR) using RMAN
) was taken from
www.in-oracle.com.
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