Re: Scalable Performace - Inserts/Updates

My understanding is that Oracle can corrupt one member of a redo log group, while the other member is written to cleanly. Why one and not the other, I do not know. However, I did get hit with redo log corruption in the past. And guess what, I believed in only hardware mirroring, so there was only one redo log member per group. Embarrassingly, I was reminded at the time by a colleague that had the redo log groups had more that one member, chances were that only one redo log member would be corrupted and the database could continue normal operation. There is no way to continue operating with a database where the one and only redo log group member is corrupt, the database must be restored from backup.

Operating a database without more than one redo log member per group is ok as long as you understand and accept the risks.

Allan

In article <3a407134.931632_at_news-server>,   nsouto_at_nsw.bigpond.net.au.nospam (Nuno Souto) wrote:
> On Tue, 19 Dec 2000 18:57:09 GMT, Allan Plesniarski
> <aplesnia_at_my-deja.com> wrote:
>
> >Software mirroring of redo log groups, ie. more than one member per
> >group, protects against one of the redo log members becoming
 corrupted
> >during the log buffer write.
> >
>
> Really? How?
>
> >
> >If hardware mirroring is used with only one redo log member per
 group,
> >the hardware will simply mirror the corruption. Whereas with
 software
> >mirroring, one member may become corrupted while the other remains
> >useable.
> >
>
> How can it become corrupt? If ORACLE corrupts it, then it's corrupt
> on both groups. If the hardware corrupts it, then group or no group
> what tells you that the hardware won't corrupt both groups?
>
> Cheers
> Nuno Souto
> nsouto_at_bigpond.net.au.nospam
> http://www.users.bigpond.net.au/the_Den/index.html
>

Sent via Deja.com
http://www.deja.com/ Received on Wed Dec 20 2000 - 11:27:07 CST