Re: Multiplexing Datafiles?

As others have already stated, there is no facility in Oracle to do this. There is, however, a good argument for this feature. Suppose Oracle issues a write request to some OS software or hardware mirrored datafile, but due to a bug (e.g. OS kernel, mirroring software, etc.), the data actually sent to one of the disks is not what Oracle passed off to the write request. This likely introduces Oracle data corruption, depending on which disk is used to satisfy a subsequent read request. Once Oracle hits the logical data corruption, ORA-1578 is reported. Oracle does not know there is some type of mirroring in place, and as far as the OS is concerned, there is no "data corruption." I have seen this exact scenario occur with multiple vendors.

If, however, the datafile was multiplexed within Oracle, two write requests would have to be issued, one for each of the two members in the group. The likelihood of both becoming logically corrupt is less than the above example. When the read request is issued, Oracle would read from one of the members of the group. If a logical corruption is detected, a read can be issued for the other member. A similar mechanism to the current multiplexed online logs.

Although the complete redo stream offers complete data protection, multiplexing datafiles offers a higher degree of availability.

Doug.

In article <8n4295$mqp$1_at_nnrp1.deja.com>,   Rob Jolliffe <rjolliffe_at_my-deja.com> wrote:
> Hi,
>
> I'm just beginning to learn Oracle, and I was reviewing some Email
> regarding Raid5 vs Raid0 performance. It seems Raid 0 is
 significantly
> better for performance - but you lose the redundancy of Raid 5 (or
 even
> Raid 1).
>
> I was trying to also determine if in a data tablespace it is possible
 to
> multiplex (mirror) datafiles the same way you can with a Redo log
 group.
> I was totally unable to determine if you are or are not.
>
> Can anyone tell me? I know you can stripe tablespaces - but can you
> mirror them? Perhaps this requires creating two tablespaces and
 somehow
> matching them?
>
> Thanks very much
>
> -Rob
>
> =============
> From the desk of Rob Jolliffe
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>

Sent via Deja.com http://www.deja.com/
Before you buy. Received on Tue Aug 15 2000 - 19:19:24 CDT