Re: Change block tracking and corruption detection in 10g

On 11/14/06, Ram Raman <veeeraman@xxxxxxxxx> wrote:

Hi all,

Some time ago there was a discussion on how we would detect the corrupt
blocks if the blocks are skipped from being read during RMAN backup because
of change block tracking.  I was in an Oracle training class and I asked the
question to the instructor. His answer was that if the block was not being
accessed it could not go corrupt. ie. If the block is changed then it is
tracked by Oracle, if it is not accessed and changed how it could go
corrupt.  Any comments?



If the sector of the brown spinning stuff that the un-accessed block lives
on
has a defect and causes a physical corruption, the database block may be
unaffected.

Or if your SAN/Disk Controller/NAS has a hiccup, something bad might happen.
( It *does* happen)

This can be used to check for corruptions

run {
   allocate channel d1 type disk;
   allocate channel d2 type disk;
   backup check logical validate database;
   release channel d1;
   release channel d2;
}

the view V$DATABASE_BLOCK_CORRUPTION will be populated if corrupt blocks are
found.

--
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist

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