John O'Neall asks:
>Can someone tell me in what case(s) the mirrored copy of the DB (and log)
>is supposed to help.
>
>I tried an experiment, since we're not yet in production. I stopped
>ADSM, then unmounted the file system on which one of the DB mirrors
>resides. Relaunching ADSM got it as far as the message
>
>ANR7850I Process 39958 has terminated on signal 13 (Write Pipe, No Reader).
>
>at which point it hung without starting any more than 2 dsmserv
>processes. It was impossible to connect an adminsitrative client and
>therefore to do anything else.
John,
I'm not sure why we aren't recovering from this error. Is it possible that
the dismounted filesystem might contain other files that either ADSM or the
operating system needs? If you can't find anything like that, you should open
a problem with IBM support.
In the mean time, try re-mounting the filesystem, then renaming the mirrored
DB copy and see if ADSM can get by that.
By the way, although the ADSM product supports the use of raw logical volumes
for database and recovery log files, we generally don't recommend their use,
as the benefits do not usually outweigh the potential problems. I don't know
whether you are using them or not, but I just thought I'd mention this.
As to what benefit mirroring provides: mirroring helps prevent loss of the
database or recovery log in the event of a media failure. This doesn't
necessarily mean that ADSM might not abend in the event of the failure, or
have problems starting up. You may have to take some kind of corrective action
in order to get ADSM started up again, depending on the nature of the problem.
For example, if there is a bad page in the primary copy of the db or log, you
might have to set MIRRORREAD LOG and/or MIRRORREAD DB to VERIFY, which will
force ADSM to look in the mirror copies for the good page, at which time all
mirrored volumes will be resynchronized. (By the way, in this example, once
ADSM is successfully restarted, you should shut it down again and set the
MIRRORREAD LOG and MIRRORREAD DB values to their original settings, as VERIFY
usually involves a performance hit. Then restart ADSM.) The point is, you've
saved yourself from the very painful dumpdb/install/loaddb/auditdb process.
Andy Raibeck
ADSM Level 2 Support
408-256-0130
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