RE: duplexing redos and archives

What measures can you do to prevent this, other than soft duplexing of online and archived redo and setting DB_BLOCK_CHECKSUM=TRUE? (Assuming this problem arises for real between your regular recovery tests!)

And when it does happen what can you / did you do (after you stopped shouting and swearing)?!

Thanks
- Bill

At 17:43 06/08/2002 -0800, you wrote:
>yeah me too.... 40 hours without sleep. Never again
>
>--- "Orr, Steve" <sorr_at_rightnow.com> wrote:
> > > Has anyone ever heard of #2 ever occuring?
> > Yeah and it hit the fan.
> >
> >
> > -----Original Message-----
> > Sent: Tuesday, August 06, 2002 4:29 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > Has anyone ever heard of #2 ever occuring? Even if possible I am not
> > aware
> > of anyone presenting a clear case of this actually happening.
> >
> > Ethan Post
> > (972) 577-6552
> > Ethan.Post_at_ps.net
> > perotdba (AIM), epost1 (Yahoo)
> > --------------------------------------------------------------------
> >
> >
> > -----Original Message-----
> > Sent: Tuesday, August 06, 2002 4:08 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > I think the logical argument is on your side as well. The Oracle
> > kernel
> > has some code path that allows it to write different things into
> > supposedly "identical" redo logs, to account for device glitches,
> > etc.
> > But this works only if you use the *Oracle* capability to multiplex
> > redo.
> >
> >
> > Cary Millsap
> > Hotsos Enterprises, Ltd.
> > http://www.hotsos.com
> >
> > Upcoming events:
> > - Hotsos Clinic, Oct 1-3 San Francisco, Oct 15-17 Dallas, Dec 9-11
> > Honolulu
> > - 2003 Hotsos Symposium on OracleR System Performance, Feb 9-12
> > Dallas
> > - Next event: NCOAUG Training Day, Aug 16 Chicago
> >
> >
> >
> > -----Original Message-----
> > Sent: Tuesday, August 06, 2002 1:44 PM
> > To: Multiple recipients of list ORACLE-L
> >
> > This may be 'old school' thinking, but I prefer to duplex my redo
> > logs.
> > Why?
> > Because there are some things that mirroring cannot protect you
> > against.
> > 1. The deletion of a redo log through human error (been there,
> > recovered
> > from it...)
> > 2. The logical corruption of a redo log (never experienced it myself,
> > but it
> > is theortically possible)
> > 3. Oracle's fault tolerance regarding the ability to function as long
> > as
> > 1
> > redo log in a group is accessible
> >
> > Considering the critical nature of the redo logs (lose one and your
> > recovery
> > is done...and perhaps your job) and their small size in relation to
> > overall
> > databse size, duplexing in a group makes sense.
> >
> > This is one of those issues where valid arguements exist on both
> > sides.
> > In
> > some ways, the logical arguements are on the side of not duplexing
> > redo
> > logs
> > that are mirrored. However, when you consider that the loss or
> > corruption of
> > a single redo log can cause the database to be unrecoverable is
> > enough
> > to
> > justify the cost of duplexing.
> >
> > Just my humble (old school) opinion
> >
> > Dan Fink
> >
> > -----Original Message-----
> > Sent: Tuesday, August 06, 2002 12:13 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > Currently we are duplexing our redo logs and archive logs through
> > oracle. We do this at the oracle level because we are using mirroring
> > (raid0?) and if we lose a redo log or archive file the database will
> > not
> > be affected.
> >
> > We will be moving to raid5 arrays in the future and are wondering
> > whether we still need to do the duplexing. Since the arrays are made
> > up
> > of data disks plus a parity disk plus a hot swap do we need to worry
> > about losing a redo log? Our sys admins are telling us we don't and I
> > tend to agree with them but we want to get other opinions on the
> > subject.
> >
> > How are shops handling this who are using raid5?
> >
> > Thanks.
> > Joe
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.com
> > --
> > Author: Joe Armstrong-Champ
> > INET: Joseph.Armstrong-Champ_at_tufts.edu
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
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Author: Bill Buchan
  INET: wbuchan_at_uk.intasys.com

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