Re: Changing to Raw Redo

Oh my,

Be careful with this, be very very careful

Let me let that ferment a bit in the back of my head; failover to a non-identical system always gives me nerves; all you need is one typo in something somewhere and boy are you in trouble.

RSH. "Bass Chorng" <bchorng_at_yahoo.com> wrote in message news:bd9a9a76.0202281444.253d49b_at_posting.google.com...
> "RSH" <RSH_Oracle_at_worldnet.att.net> wrote in message
news:<Wagf8.4412$106.252464_at_bgtnsc05-news.ops.worldnet.att.net>...
> > Uh, remapping devices and things would be a problem; but more to the
point,
> > why do redo in raw partitions? Redos are written to serially, till
they're
> > filled, then a log switch, etc. Have you done some analysis that would
lead
> > you to conclude that putting your redo log files on raw partitions would
> > alleviate a particular problem?
>
> The decision was based on a series of tests. There are a number of
> in-depth documents recommending raw for redo. You can check Steve Adam's
> site (ixora.com.au). He has a very detailed document on this. I also
have
> a copy of Oracle's internal performance tuning literature which suggests
> the same.
>
> My own tests showed 50% of deduction on "redo write time" after
switching
> to raw. I performed 5 tests before and 5 tests after and the numbers are
> very consistently convincing. Of course the tests are a bit unrealistic,
> and it does show you the magnified difference. In real life the
difference
> will definitely be smaller, but the point is, there IS a difference
> attractive enough to go thru the inconvenience of raw. At least I am
> convinced.
>
> >
> > As far as propagation by (I assume you mean) Oracle Standby, I'm not
sure
> > whether it supports raw partitions but I'd be surprised if it did not;
you
> > never know, though...
> >
>
> I know Standby supports raw redo. It has no difference than primary.
> In fact, while a standby is recovering, it does NOT have any redo
> logs. As it deos not generate redo while recovering. But when you open
> standby, it has to create redo logs at that point. And it is at that
point
> you will see failure, because the raw paths do not exist on the standby
> box. So my question is, can I use a symbolic link to point to the raw
> chunk in the first place, so when I open the standby, I can point the
> link to another raw chunk on the standby box ?
>
> The other way around, I believe, is to create controlfile,( instead of
> using standby controlfile ) and modify the redo paths in there, and
> open resetlogs. Does anybody know if this works ?
>
> Trying to drop the logfile and add new one does not work, because
database
> is not open and you can not open the database unless Oracle can create
the
> redo logs as specified in the standby controlfiles.
>
> > and what is your platform?
>
> 8.1.7 on Solaris 2.7
Received on Fri Mar 01 2002 - 12:17:47 CST