Norwood,
Just to add to your comments, I think the biggest benefit of
multiplexing redo logs, is that any problems/issues with a
member will be documented in the alertSID.log. This however
will not occur in the case of when the redo logs are only O-S
mirrored. Unless one wears two hats namely that of a DBA and
SysAdmin, and/or has access to syslogs (logs of the O-S) and
monitor them proactively, multiplexing is a more effective
method of managing Oracle's redo logs.
This is because if a member of an O-S mirror fails, there are no
alertSID.log entries generated and if errors to syslogs are not
proactively monitored, you could find yourself in big trouble
when the second member in the O-S mirror also fails. When that
happens, you know you have trouble with the redo log disk
volumes, but it is too late.
I have had customers who mirrored their redo logs and did not
follow up by proactively monitoring their syslogs and had
mirrored volume failures. The fun/scary part is that some of
the failures went undetected for over 5 weeks (on production
databases). The customer was lucky that Mr. Murphy was not
around the corner to show his brilliance...;-)
Best Regards,
Gaja.
- Norwood Bradly A <Bradley.A.Norwood_at_M1.IRSCOUNSEL.TREAS.GOV>
wrote:
> Robyn:
>
> Have not yet read that tip from Steve Adams, but I value his
> opinions very
> highly.
>
> However, Oracle seems to go with multiplexing as shown by
> their caveat
> regarding o/s or hardware corruption:
>
> In my shop, we do both mirroring and multiplexing
>
> Multiplexing Online Redo Log Files
> Oracle provides the capability to multiplex an instance's
> online redo log
> files to safeguard against damage.
> You can also mirror your redo logs at the O/S level, but in so
> doing you run
> the risk of O/S or hardware induced corruption. In most cases,
> multiplexing
> of online logs is best.
>
>
> -----Original Message-----
> Sent: Monday, June 12, 2000 11:52 AM
> To: Multiple recipients of list ORACLE-L
>
>
>
>
> listers,
>
> Reading through Steve Adams web site, I came across
> the tip that says redo logs should be mirrored or
> multiplexed, but there is no need to do both. The
> explanation makes sense, but I have never run a
> production database without multiplexing redo logs,
> and the thought of doing so is a little scary!! I
> wanted to find out how many other DBA's have taken
> this approach, and if you've tried it, how much of
> performance difference have you seen? Is there any
> increased risk of data loss?
>
> TIA ... Robyn Sands
>
>
> --
> Author:
> INET: rsands_at_lendleaserei.com
>
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> Author: Norwood Bradly A
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Gaja Krishna Vaidyanatha | 3460 West Bayshore Road,
Manager - Integration | Palo Alto, CA 94303
& Consulting Services | gaja_at_brio.com
Global Alliances | (650)-565-4442
Brio Technology | www.brio.com
"Opinions and views expressed are my own and not of Brio Technology"
Received on Mon Jun 12 2000 - 16:35:44 CDT
