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RE: dbv - Found block already marked corrupted

From: Bobak, Mark <Mark.Bobak_at_il.proquest.com>
Date: Mon, 2 Feb 2004 10:12:42 -0500
Message-ID: <4C9B6FDA0B06FE4DAF5918BBF0AD82CF03B451F1@bosmail00.bos.il.pqe>


Actually, there is a utility that can do what you want. It's called bbed. But, since it's possible, even easy, to not only shoot yourself in the foot, but actually blow an entire leg off, that's all I'll say about it. ;-)

-Mark

Mark J. Bobak
Oracle DBA
ProQuest Company
Ann Arbor, MI
"Imagination was given to man to compensate him for what he is not, and a sense of humor was provided to console him for what he is." --Horace Walpole

-----Original Message-----
From: Kaing, Leng [mailto:Leng.Kaing_at_team.telstra.com]=20 Sent: Sunday, February 01, 2004 8:55 PM
To: oracle-l_at_freelists.org
Subject: Re: dbv - Found block already marked corrupted Importance: High

Mladen,

You're of course right again! I've done all I can - rebuilt the index, =
=3D

dropped the index, created the index, yet the block is still reported as
=3D

already marked corrupted. And this time when I do a cdba it points to an
=3D

empty block. Why isn't there a utility to unmark an empty block that was
=3D

previoiusly "marked corrupted"!

I've almost lost faith in this utility now (or maybe I already have!) =
=3D

We've just scheduled a weekly job to do a dbv to detect coruption. Now =
=3D

I'm getting tons of blocks marked corrupted even though they're clean =
=3D

(I know because we do a drop and import from production every night!) It
=3D

would take me forever to make a list and say "if this block for this =3D database comes up, ignore it" ARGH!!!

Yes, I'm waiting for the unflag utility too.=3D20

Leng.



Date: Fri, 30 Jan 2004 16:02:41 -0500
From: Mladen Gogala <mladen_at_wangtrading.com> Subject: Re: dbv - Found block already marked corrupted

On 01/30/2004 03:46:04 PM, Tim Gorman wrote:

> One further question, though...
>=3D20
> >> Of course, if someone knows a utility to un-flag a block I'm all
> ears.
>=3D20
> Why would anyone want to "unflag" a block that has been flagged as
> corrupt?
> I'm all ears for that...  :-)
>=3D20
> -Tim


Actually, not all corrupt blocks are the same. The definition of a =3D20 corrupt block is "a block with a bad checksum". These bad checksums are mostly caused by software. I have a ton of experience with "corrupt =
=3D20

blocks" which came into being after copying production database to =3D20 development database using BCVs. This means hot backup and instance =
=3D20

recovery. For the reasons of speed, the tables with the computed data
=3D20

were created with "NOLOGGING" attribute and when access was attempted
=3D20

in the cloned instance, oracle started screaming about "corrupted =3D20 blocks". When the table was truncated and the data computed again, the
=3D

"corruption" was gone. In other words, so called "corrupt blocks" can simply be flagged "honest" and reused, if they're empty.



Leng Kaing
Email: leng.kaing_at_team.telstra.com
Phone: +61-3-9203-7589
Mobile: +61-417-371-348

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Received on Mon Feb 02 2004 - 09:12:42 CST

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