Re: dbv - Found block already marked corrupted

From: Kaing, Leng <Leng.Kaing_at_team.telstra.com>
Date: Mon, 2 Feb 2004 12:54:36 +1100
Message-ID: <778AA0998E7BD411879D0008C7246DF40FB0546B@ntmsg0093.corpmail.telstra.com.au>

Mladen,

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

dropped the index, created the index, yet the block is still reported as =
already marked corrupted. And this time when I do a cdba it points to an =
empty block. Why isn't there a utility to unmark an empty block that was =

previoiusly "marked corrupted"!

I've almost lost faith in this utility now (or maybe I already have!) = We've just scheduled a weekly job to do a dbv to detect coruption. Now = I'm getting tons of blocks marked corrupted even though they're clean = (I know because we do a drop and import from production every night!) It = would take me forever to make a list and say "if this block for this = database comes up, ignore it" ARGH!!!

Yes, I'm waiting for the unflag utility too.=20

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...

>=20

> >> Of course, if someone knows a utility to un-flag a block I'm all
> ears.

>=20

> Why would anyone want to "unflag" a block that has been flagged as
> corrupt?
> I'm all ears for that... :-)

>=20
> -Tim

Actually, not all corrupt blocks are the same. The definition of a =20 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 =20 blocks" which came into being after copying production database to =20 development database using BCVs. This means hot backup and instance =20 recovery. For the reasons of speed, the tables with the computed data =20 were created with "NOLOGGING" attribute and when access was attempted =20 in the cloned instance, oracle started screaming about "corrupted =20 blocks". When the table was truncated and the data computed again, the =

"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 Sun Feb 01 2004 - 19:54:36 CST