Date: Mon, 2 Feb 2004 11:00:06 -0500
From: Mladen Gogala <mladen@wangtrading.com>
To: oracle-l@freelists.org
Subject: Re: dbv - Found block already marked corrupted
Message-ID: <20040202160006.GA27080@mladen.wangtrading.com>
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In-Reply-To: <4C9B6FDA0B06FE4DAF5918BBF0AD82CF03B451F1@bosmail00.bos.il.pqe> (from Mark.Bobak@il.proquest.com on Mon, Feb 02, 2004 at 10:12:42 -0500)
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Actually, bbed is quite well documented at Rama Velpuri's place.
The utility itself, is, however, password protected. If you want
to read more about that oracle hacking utility, go to:

http://www.fors.com/velpuri2/Oracle%20block%20structure/BBED

I tried obtaining the password, to no avail. It is quite well  
protected, and with a reason. This utility makes it possible to
edit database blocks directly. I would never want to use DUL or
BBED if I don't really, really have to.


On 02/02/2004 10:12:42 AM, "Bobak, Mark" wrote:
> 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@team.telstra.com]=20
> Sent: Sunday, February 01, 2004 8:55 PM
> To: oracle-l@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@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@team.telstra.com
> Phone: +61-3-9203-7589
> Mobile: +61-417-371-348
> 
> ----------------------------------------------------------------
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