Andy,

Thanks for the detailed scoop.  This will hopefully give me the
ammunition to get more disk space to turn mirroring back on.

Tina

> -----Original Message-----
> From: Andrew Raibeck [SMTP:storman AT US.IBM DOT COM]
> Sent: Wednesday, June 10, 1998 2:48 PM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Re: Recovery log error ANR0209E on server startup
>
> Usually I recommend using ADSM mirroring. When mirroring is controlled
> by
> something other than ADSM, that "something" (hardware or operating
> system)
> isn't smart enough to detect partial page writes that could result in
> corruption; it just automatically mirrors the volumes, corruption and
> all.
>
> ADSM mirroring with the MIRRORWRITE LOG SEQUENTIAL option in the
> server options
> file is intended to prevent partial page writes from making it to all
> copies of
> the recovery log. With MIRRORWRITE LOG SEQUENTIAL, a page has to be
> successfully written to one copy of the recovery log before it will be
> written
> to the other. So if ADSM is in the middle of writing a page to one of
> the
> recovery log copies when it goes down, the update to the other
> copy(ies) does
> not occur. Upon restart, if ADSM can't read the data from one of the
> recovery
> log copies, it should be able to get it from another, then
> resynchronize all
> copies.
>
> One caveat with this is that there may be a performance penalty with
> MIRRORWRITE LOG SEQUENTIAL (as opposed to MIRRORWRITE LOG PARALLEL).
> Writing in
> parallel may offer better performance, but it won't prevent partial
> page writes
> from being written to all log copies. So you should run some
> performance tests
> before committing to the SEQUENTIAL write strategy. I think I saw
> someone post
> once that they saw only a negligible difference, but it's best to see
> how it
> works in your shop.
>
> By the way: by default the database writes sequentially and the
> recovery log
> writes in parallel.
>
> Andy
>
> Andy Raibeck
> IBM Storage Systems Division
> ADSM Client Development
> e-mail: storman AT us.ibm DOT com
>
>
>
> ADSM-L AT VM.MARIST DOT EDU on 06/10/98 12:32:03 PM
> Please respond to ADSM-L AT VM.MARIST DOT EDU
> To: ADSM-L AT VM.MARIST DOT EDU
> cc:
> Subject: Recovery log error ANR0209E on server startup
>
>
> Our configuration is ADSM 2.1.5.15 on AIX 4.1.5.  Our RS6000 died
> today