On Thursday, Sep 4, 2003, at 04:04 Australia/Sydney, Jurjen Oskam wrote:

On Wed, Sep 03, 2003 at 01:02:02PM -0400, Lawrence Clark wrote:

Richard Sims wrote:

aggravated by a prevailing device problem, I am wondering if you have
MIRRORWrite in effect for your DB and/or Recovery Log...with
Sequential
writing?

RAID-5 protection on our TSM DB.

That's either OS or storage system mirroring, not TSM mirroring. The
TSM
documentation implies that TSM mirroring will protect against certain
failures
against which OS or storage system mirroring will not protect. (I think
this is a shortcoming of TSM, but not so bad I can't live with it. :-)
)

The only instances I can think of where TSM sequential mirroring will
beat
a problem is an OS crash or power failure when using either OS software
mirroring with a parallel write policy, or software RAID 5. In these
cases,
TSM mirroring will (should?) save the day. This isn't a flaw in TSM,
but in
the underlying layers from the OS down.

Cheers,
--
Paul Ripke
Unix/OpenVMS/TSM/DBA
101 reasons why you can't find your Sysadmin:
68: It's 9AM. He/She is not working that late.
-- Koos van den Hout