Block Media Recovery with RMAN

This document will detail a block media recovery scenario using a RMAN disk based backup. If you need a document for configuring RMAN see the post Setting up RMAN for backup and recovery using Database Control

Scenario:

You receive an email from a user reporting the error below when attempting to access a table.

SQL> select * from payroll;
select * from payroll
              *
ERROR at line 1:
ORA-01578: ORACLE data block corrupted (file # 6, block # 1291)
ORA-01110: data file 6: '/u02/app/oracle/oradata/orcl/test.dbf'


SQL>

Action:

Since we have the file number and the corrupted block number we can use RMAN to perform block media recovery on the file. Note that the database can remain open during block media recovery. Below is the output from using the blockrecover command in RMAN.

[oracle@ora1 ~]$ rman

Recovery Manager: Release 11.2.0.1.0 - Production on Wed Apr 21 10:23:11 2010

Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.

RMAN> connect target /

connected to target database: ORCL (DBID=1239150297)

RMAN> blockrecover datafile 6 block 1291;

Starting recover at 21-APR-10
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=40 device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=38 device type=DISK
searching flashback logs for block images until SCN 1339488
finished flashback log search, restored 0 blocks

channel ORA_DISK_1: restoring block(s)
channel ORA_DISK_1: specifying block(s) to restore from backup set
restoring blocks of datafile 00006
channel ORA_DISK_1: reading from backup piece /u03/app/oracle/oradata/orcl/backup/1clblq5q_1_1
channel ORA_DISK_1: piece handle=/u03/app/oracle/oradata/orcl/backup/1clblq5q_1_1 tag=TAG20100421T084546
channel ORA_DISK_1: restored block(s) from backup piece 1
channel ORA_DISK_1: block restore complete, elapsed time: 00:00:02

starting media recovery
media recovery complete, elapsed time: 00:00:01

Finished recover at 21-APR-10

RMAN>

Now we can check the table again and see that the corrupt block has been fixed.

SQL> select count(*) from payroll;

  COUNT(*)
----------
         5

SQL>

Note: When you discover a corrupted block you should check all datafiles for corruption as there could be other corrupted blocks. You can use the dbverify utility or perform a RMAN backup of the entire database. RMAN will exit with an error when a corrupt block is found.

[oracle@ora1 ~]$ rman

Recovery Manager: Release 11.2.0.1.0 - Production on Wed Apr 21 10:32:19 2010

Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.

RMAN> connect target /

connected to target database: ORCL (DBID=1239150297)

RMAN> backup database plus archivelog delete input;


Starting backup at 21-APR-10
current log archived
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=47 device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=38 device type=DISK
channel ORA_DISK_1: starting archived log backup set
channel ORA_DISK_1: specifying archived log(s) in backup set
input archived log thread=1 sequence=10 RECID=18 STAMP=716898757
channel ORA_DISK_1: starting piece 1 at 21-APR-10
channel ORA_DISK_1: finished piece 1 at 21-APR-10
piece handle=/u03/app/oracle/oradata/orcl/backup/1hlbm0e6_1_1 tag=TAG20100421T103238 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
channel ORA_DISK_1: deleting archived log(s)
archived log file name=/u02/app/oracle/oradata/orcl/arch/1_10_716298144.dbf RECID=18 STAMP=716898757
Finished backup at 21-APR-10

Starting backup at 21-APR-10
using channel ORA_DISK_1
using channel ORA_DISK_2
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=/u02/app/oracle/oradata/orcl/system01.dbf
input datafile file number=00007 name=/u03/app/oracle/oradata/orcl/dbfs01.dbf
input datafile file number=00002 name=/u02/app/oracle/oradata/orcl/sysaux01.dbf
channel ORA_DISK_1: starting piece 1 at 21-APR-10
channel ORA_DISK_2: starting full datafile backup set
channel ORA_DISK_2: specifying datafile(s) in backup set
input datafile file number=00003 name=/u02/app/oracle/oradata/orcl/undotbs01.dbf
input datafile file number=00005 name=/u02/app/oracle/oradata/orcl/example01.dbf
input datafile file number=00006 name=/u02/app/oracle/oradata/orcl/test.dbf
channel ORA_DISK_2: starting piece 1 at 21-APR-10
RMAN-03009: failure of backup command on ORA_DISK_2 channel at 04/21/2010 10:32:55
ORA-19566: exceeded limit of 0 corrupt blocks for file /u02/app/oracle/oradata/orcl/test.dbf
continuing other job steps, job failed will not be re-run
channel ORA_DISK_2: starting full datafile backup set
channel ORA_DISK_2: specifying datafile(s) in backup set
input datafile file number=00004 name=/u02/app/oracle/oradata/orcl/users01.dbf
channel ORA_DISK_2: starting piece 1 at 21-APR-10
channel ORA_DISK_2: finished piece 1 at 21-APR-10
piece handle=/u03/app/oracle/oradata/orcl/backup/1klbm0eo_1_1 tag=TAG20100421T103240 comment=NONE
channel ORA_DISK_2: backup set complete, elapsed time: 00:00:15
channel ORA_DISK_1: finished piece 1 at 21-APR-10
piece handle=/u03/app/oracle/oradata/orcl/backup/1ilbm0e8_1_1 tag=TAG20100421T103240 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:01:51
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of backup plus archivelog command at 04/21/2010 10:34:31

RMAN-03009: failure of backup command on ORA_DISK_2 channel at 04/21/2010 10:32:55
ORA-19566: exceeded limit of 0 corrupt blocks for file /u02/app/oracle/oradata/orcl/test.dbf

RMAN> 
RMAN> 

The backup failed because RMAN detected at least 1 corrupt block in the file /u02/app/oracle/oradata/orcl/test.dbf. That is the only file that has corrupt blocks. Unfortunately RMAN does not tell us how many blocks or which blocks are corrupt. The dbverify utility will tell you how many blocks are corrupt and identify the block numbers.

[oracle@ora1 ~]$ dbv file=/u02/app/oracle/oradata/orcl/test.dbf

DBVERIFY: Release 11.2.0.1.0 - Production on Wed Apr 21 10:50:59 2010

Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.

DBVERIFY - Verification starting : FILE = /u02/app/oracle/oradata/orcl/test.dbf
Page 1292 is marked corrupt
Corrupt block relative dba: 0x0180050c (file 6, block 1292)
Bad header found during dbv: 
Data in bad block:
 type: 67 format: 7 rdba: 0x6e697470
 last change scn: 0x7369.68742067 seq: 0x20 flg: 0x62
 spare1: 0x72 spare2: 0x75 spare3: 0x6b63
 consistency value in tail: 0x00000001
 check value in block header: 0x6f6c
 block checksum disabled

Page 1296 is marked corrupt
Corrupt block relative dba: 0x01800510 (file 6, block 1296)
Bad header found during dbv: 
Data in bad block:
 type: 99 format: 7 rdba: 0x69747075
 last change scn: 0x6968.7420676e seq: 0x73 flg: 0x20
 spare1: 0x72 spare2: 0x72 spare3: 0x636f
 consistency value in tail: 0x00000001
 check value in block header: 0x6c62
 block checksum disabled



DBVERIFY - Verification complete

Total Pages Examined         : 1440
Total Pages Processed (Data) : 1037
Total Pages Failing   (Data) : 0
Total Pages Processed (Index): 0
Total Pages Failing   (Index): 0
Total Pages Processed (Other): 249
Total Pages Processed (Seg)  : 0
Total Pages Failing   (Seg)  : 0
Total Pages Empty            : 152
Total Pages Marked Corrupt   : 2
Total Pages Influx           : 0
Total Pages Encrypted        : 0
Highest block SCN            : 1341204 (0.1341204)
[oracle@ora1 ~]$ 

Here we see the two blocks that are corrupt and we can easily perform block media recovery on those blocks using the procedure outlined earlier.

Leave a Reply

Your email address will not be published. Required fields are marked *