Re: RMAN impact
- From: "Mark Brinsmead" <pythianbrinsmead@xxxxxxxxx>
- To: "Christian Antognini" <Christian.Antognini@xxxxxxxxxxxx>
- Date: Tue, 24 Oct 2006 22:08:07 -0600
Chris,
Perhaps I have misread the documentation. Here is the relevant section
of the 10g "Backup and revoery Reference":
CHECK LOGICAL
==================
Tests data and index blocks that pass physical corruption checks for logical
corruption, for example, corruption of a row piece or index entry. If RMAN
finds logical corruption, then it logs the block in the alert.log and server
session trace file.
If the sum of physical and logical corruptions detected for a file is no
more
than its MAXCORRUPT setting, then the backup command completes, and
V$DATABASE_BLOCK_CORRUPTION is populated with any corrupt block
ranges. If there are more thanMAXCORRUPT corrupt blocks, then the command
terminates without updating the view and no output file is created for the
backup.
If the initialization parameter DB_BLOCK_CHECKSUM=TRUE, and if
MAXCORRUPT and NOCHECKSUM are not set, then specifying CHECK LOGICAL
detects all types of corruption that are possible to detect.
Note: The MAXCORRUPT setting specifies the total number of physical and
logical corruptions permitted on a file.
=========================================================
Those are pretty strong words, even coming from an Oracle manual. ;-)
It is my understanding that an RMAN "BACKUP VALIDATE" with "CHECK LOGICAL"
can, indeed, detect the sorts of corruption you are referring to. I've even
used it for
such purposes on a couple occasions -- but since the results were "negative"
I can't
say for certain that it really works... ;-)
On 10/24/06, Christian Antognini <Christian.Antognini@xxxxxxxxxxxx> wrote:
Hi Mark
Just a couple of comments...
...
Be carefull... CHECK LOGICAL doesn't cover all type of logical
corruptions. Inconsistencies, e.g. ORA-01499, are *not* detected. AFAIK
ANALYZE is the only tool able to discover them.
Regards,
Chris
--
Cheers,
-- Mark Brinsmead
Senior DBA,
The Pythian Group
http://www.pythian.com/blogs
Other related posts:
