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TNS:packet writer failure
see ORA-12699
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RE: Identifying the content of a corrupted block in system tablespace

Vlado Barun


Just a quick summary on how I resolved this problem (see below for the
problem definition).

I used a stored proc to dynamically execute a "select /*+ full(t)
noparallel(t) */" against all appropriate objects to identify the objects
that were affected. The result was 1 synonym, 2 views and 3 tables were
affected. Fortunately the 3 tables contained old audit data and were not
needed anymore, and the views and synonym could easily be recreated.

So, I set event = "10231 trace name context forever, level 10" to export
all data, except the corrupted block. However, export failed with an ora-600
on the export, basically saying that it's trying to export a table for which
it can't find it's location.
After further research, I added "and o$.name not in ('PS_AUDIT_0000222',
'PS_AUDIT_0000223', 'PS_AUDIT_0000224' )" to the export views sys.EXU8CLU
and SYS.EXU8TAB, thus telling export not to even try to deal with the 3
affected tables. It worked and the rest is the standard exp/imp story...

Thank you for all of your help.

-----Original Message-----
From: oracle-l-bounce@(protected)]
On Behalf Of Vlado Barun
Sent: Thursday, January 06, 2005 6:24 PM
To: oracle-l@(protected)
Subject: Identifying the content of a corrupted block in system tablespace

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

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:

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

----- ------------ ------------ ---------------- -------- ------
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