Re: Question on Corrupted blocks

Ashoke,

Please consider "dbv" as more of a *screening* for block corruption than a definitive diagnosis. For one thing, "dbv" does not connect to the database instance, so it cannot determine whether the buffer in the Buffer Cache in the SGA is also corrupted.

To determine if a datafile block is truly corrupted, please connect to SQL*Plus as SYSDBA and run the following...

    ALTER SYSTEM DUMP DATAFILE [ /file#/ | /'filename'/ ] BLOCK [     /block#/ | MIN /block#/ BLOCK MAX /block#/ ]

...which in your situation might mean running the following commands, based on "dbv" output...

    alter system dump datafile 40 block 35586;

    alter system dump datafile40 block 35598;
    alter system dump datafile40 block 35599;
    alter system dump datafile40 block 35600;
    alter system dump datafile40 block 35601;
    alter system dump datafile40 block 35603;
    alter system dump datafile40 block 35605;
    alter system dump datafile40 block 35607;
    alter system dump datafile40 block 35834;
    alter system dump datafile40 block 36579;

...or maybe something like this instead...

    alter system dump datafile 40 block min 35586 block max 36579;

...but for that you'd have to be careful only to pay attention to the blocks listed above as corrupted within that range from 35586..36579, of course.

The dumped block information will go to a trace file in your USER_DUMP_DEST, so it might be wise to first run a command like "alter session set tracefile_identifier = dump" so that the trace file(s) generated from your ALTER SYSTEM DUMP will have the file-name suffix of "_DUMP.trc", making it easier to identify them inside the USER_DUMP_DEST directory on the database server.

If the indicated database blocks are indeed corrupted, then the output in the trace file will state so. If instead the ALTER SYSTEM DUMP command does not list the block as corrupted, then it was a "false positive" from the "dbv" program.

Hope this helps...

-Tim

On 5/24/17 15:10, Ashoke Mandal wrote:
> Hello,
>
> I shutdown the database, ran dbverify($ORACLE_HOME/bin/dbv) and it
> reported the following block corruption in the respective logfile (as
> listed below - 1 through 4).
>
> But "select * from v$database_block_corruption;" doesn't return any rows.
> Q1. Could you provide me any idea what are the possible cause for
> these corruption?
> Q2. What is best way to check for such block corruption before I
> upgrade a production database?
> Q3. Is it possible there might be some corrupt blocks but we don't
> receive any complain from anywhere (user or alert log etc.)?
>
>
> 1. $ORACLE_HOME/bin/dbv file=/u03/oradata/file_1_ind_idx02.dbf
> feedback=100 logfile=/<logfile_location>/file_1_ind_idx02.log
> blocksize=8192
>
> Corrupt block relative dba: 0x0a80271a (file 42, block 10010)
> Total Pages Marked Corrupt : 1
>
> 2. $ORACLE_HOME/bin/dbv file=/u03/oradata/file_2_data.dbf feedback=100
> logfile=/<logfile_location>/file_2_data.log blocksize=8192
>
> Corrupt block relative dba: 0x0a008b02 (file 40, block 35586)
> Corrupt block relative dba: 0x0a008b0e (file 40, block 35598)
> Corrupt block relative dba: 0x0a008b0f (file 40, block 35599)
> Corrupt block relative dba: 0x0a008b10 (file 40, block 35600)
> Corrupt block relative dba: 0x0a008b11 (file 40, block 35601)
> Corrupt block relative dba: 0x0a008b13 (file 40, block 35603)
> Corrupt block relative dba: 0x0a008b15 (file 40, block 35605)
> Corrupt block relative dba: 0x0a008b17 (file 40, block 35607)
> Corrupt block relative dba: 0x0a008bfa (file 40, block 35834)
> Corrupt block relative dba: 0x0a008ee3 (file 40, block 36579)
> Total Pages Marked Corrupt : 10
>
> 3. $ORACLE_HOME/bin/dbv file=/u03/oradata/file_3_idx01.dbf
> feedback=100 logfile=/<logfile_location>/file_3_idx01.log blocksize=8192
>
> mdl_ind_medium_idx01.log:Corrupt block relative dba: 0x090075a5 (file
> 36, block 30117)
> mdl_ind_medium_idx01.log:Total Pages Marked Corrupt : 1
>
> 4. $ORACLE_HOME/bin/dbv file=/u03/oradata/file_3_ind_large_idx01.dbf
> feedback=100 logfile=/<logfile_location>/file_3_ind_large_idx01.log
> blocksize=8192
>
> wip_ind_large_idx01.log:Corrupt block relative dba: 0x02c0f581 (file
> 11, block 62849)
> wip_ind_large_idx01.log:Corrupt block relative dba: 0x02c0f583 (file
> 11, block 62851)
> wip_ind_large_idx01.log:Corrupt block relative dba: 0x02c0f586 (file
> 11, block 62854)
> wip_ind_large_idx01.log:Total Pages Marked Corrupt : 3
>
> Thanks,
> Ashoke

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