Re: DB mirroring

From: Stephane Faroult <sfaroult_at_roughsea.com>
Date: Tue, 13 Jul 2004 17:12:06 +0200
Message-Id: <200407131512.i6DFC6Zs032287@webmail.nexlink.net>

Morten,

Nothing to add to your comment about RAC.

Concerning Dataguard : if I understand well, your two servers are accessed symmetrically ? In that case, I am afraid that Dataguard isn't an option. With Dataguard, one of the databases is either dormant (warming up) or, at best, read-only. DDL passes through, but the tests if have carried out with Oracle 9.2 on the logical standby have left me unconvinced (some DDL doesn't pass through - RENAME - and it never took me long before hitting an ORA-600).Hopefully it will have improved in 10g but I haven't tried it yet.

To me, your best option is symmetrical replication, but with DDL activity it's going to be a nightmare. Moreover, I am not convinced that the overhead induced by replication (and I am saying nothing about administration) will not offset the advantage of having two machines. Perhaps that a bigger machine and a smaller one used for standby may in the end be both simpler andmore effective.

Also, you may consider harware mirrorring (thinking about features such as EMC's SRDF).

Regards,

Stephane Faroult

On Tue, 13 Jul 2004 16:40 , Morten <lists_at_kikobu.com> sent:

Hi.

I have two servers A and B. They are physically separated, and are only allowed to communicate over LAN (ie. no shared storage).

If one server dies, clients should access the other, so they need to be in sync. So far I've found the following options for making a fail-over system for Oracle (9i2 BTW):

RAC - this requires shared storage as far as I can tell from the whitepaper.
Oracle Data Guard w. primary/secondary servers. Requires operator intervention upon failure at the primary host. If this is acceptable, it's still not an optimal solution as we can expect lots of structural changes to the DB (new tables, altered tables, new/dropped indexes etc).

What other options are there? Is there a "mirror all ddl+dml operations on this DB to that DB" option?

Any tips greatly appreciated,

Morten

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Received on Tue Jul 13 2004 - 10:09:45 CDT