RMAN Corrupted Blocks Identification

From: "Slava Zayarny" <Slava.Zayarny@xxxxxxx>
To: <Oracle-L@xxxxxxxxxxxxx>
Date: Mon, 4 Apr 2005 10:57:08 -0400
Hello list,

I'm trying to create a test scenario to understand what RMAN
construes to be a "corrupted" block.  The initial assumption
is that its "backup validate check logical" command should
identify such blocks. =20

Here's the test I ran.

Environment:

HP-UX 11.11
Oracle 9.2.0.6

Test Sequence:

1 Run whole database backup with RMAN (ARCHIVELOG)

2 Identify a table segment, block to corrupt:
=09
SQL> select file_id,block_id,tablespace_name from dba_extents where =
segment_name =3D 'STATUS';

   FILE_ID   BLOCK_ID TABLESPACE_NAME
---------- ---------- ------------------------------
        12        265 REACTOR5_1

SQL> select file#,name from v$Datafile where file#=3D12;

     FILE# NAME
---------- ---------------------------------------------------
        12      /PERF/agentdb/oradata/PERF/REACTOR5_1.dbf

3 Overwrite identified block

./corrupt.ksh /PERF/agentdb/oradata/PERF/REACTOR5_1.dbf 265
0+1 records in
0+1 records out

more corrupt.ksh

#!/usr/bin/ksh

FILE=3D${1:?'Parameter 1 should be set to file name'}
BLOCK=3D${2:?'Parameter 2 should be set to the block to be corrupted'}

dd of=3D$FILE bs=3D8192 conv=3Dnotrunc oseek=3D$BLOCK << EOF
CORRUPT_by_intent
EOF

4 Shutdown immediate, then startup

5 Run select on the corrupted segment:

SQL> select count(*) from reactor5.status;

  COUNT(*)
----------
        44

6 "Backup validate" affected tablespace with RMAN:

RMAN> backup validate check logical tablespace REACTOR5_1;

Starting backup at 04-APR-2005 10:31:13
using channel ORA_DISK_1
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=3D00012 =
name=3D/PERF/agentdb/oradata/PERF/REACTOR5_1.dbf
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 04-APR-2005 10:31:15

RMAN>=20

7 Check v$database_block_corruption view:

SQL> select * from v$database_block_corruption;

     FILE#     BLOCK#     BLOCKS CORRUPTION_CHANGE# CORRUPTIO
---------- ---------- ---------- ------------------ ---------
        12        265          1                  0 FRACTURED

QUESTION:=20

Why doesn't RMAN identify block corruption with "backup validate"
while still registering block corruption in v$database_block_corruption?


Cheers,

Slava Zayarny
Oracle DBA
SAS Institute Inc

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RMAN Corrupted Blocks Identification

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