Identifying the content of a corrupted block in system tablespace

From: Vlado Barun <vlado_at_cadre5.com>
Date: Thu, 6 Jan 2005 20:23:33 -0600
Message-Id: <200501070223.j072Nih45433@cadre5.com>

I have a corrupted block in the system tablespace. I used the standard query to identify the object that the block but it failed:  

SQL>
  1 SELECT segment_name

  2      , segment_type
  3      , owner
  4      , tablespace_name
  5      , block_id
  6      , blocks

  7 FROM sys.dba_extents
  8 WHERE file_id = 1
  9* AND 8002 BETWEEN block_id and block_id + blocks -1 FROM sys.dba_extents

         *
ERROR at line 7:
ORA-01578: ORACLE data block corrupted (file # 1, block # 8002) ORA-01110: data file 1: '/u100/oradata/fstst/system01.dbf'  

Then I did this:
ALTER SESSION SET EVENTS '10231 TRACE NAME CONTEXT FOREVER, LEVEL 10';   select owner

, segment_name
, segment_type
, tablespace_name
, block_id
, blocks

from dba_extents
where file_id=1
and block_id in (

        select max(block_id)
        from dba_extents
        where file_id=1
        and block_id <= 8002

);  

OWNER SEGMENT_NAME SEGMENT_TYPE TABLESPACE_NAME BLOCK_ID BLOCKS

----- ------------ ------------ ---------------- -------- ------
SYS   C_OBJ#       CLUSTER      SYSTEM           7978         25
 

So, the object that the corrupt block belongs to is c_obj#.  

Is that correct?  

If so, and since c_obj# stores data about objects (metadata), it basically means that I can not access the object whose metadata is in that block. So, I'm trying to identify which object is lost. For example, if it's just an index, I should be able to export all the objects from database into a new database and rebuild the index, and resolve the corruption in that way. Any idea how I can identify the object whose metadata is lost?  

I'm aware that Oracle support should be contacted, however a friend of mine asked me to look into this before they contact Oracle Support since they don't have a support contract anymore... BTW, this is 8.0.6, they identified this problem 3 months ago in their Peoplesoft application, and of course they don't have a good backup from which to recover...  

Vlado Barun, M.Sc.

Mobile: 865 335 7652

AIM: vbarun2  

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Received on Thu Jan 06 2005 - 20:19:09 CST