Pete Sharman <peter.sharman_at_oracle.com> wrote in message news:<adp94f02c1d_at_drn.newsguy.com>...
> In article <9fe1f2ad.0206061053.3ea16d73_at_posting.google.com>,
> laredotornado_at_zipmail.com says...
> 1. Machine failover can be handled in a variety of different mechanisms.
> Usually, it requires a cluster at the hardware level. You can then use failover
> at the OS level (node 2 takes up the IP address of node 1, and you manually
> restart the database). An alternative is to use OPS/RAC. These technologies
> allow you to AUTOMATICALLY fail the database over, and optionally continue
> queries or sessions on the second node. This leads to lower downtime than the
> manual restart mechanism. I notice you mention Oracle8 in your posting. OPS is
> the technology in Oracle8 that allows that. It's great for high availability
> but can be challenging to get scalability out of without additional work (note I
> said "challenging", not "impossible"). If 9i was a possibility, I would
> definitely recommend it to allow the use of RAC which is much more
> straightforward to get high availability AND scalability from.
>
> 2. Site failover can be handled by advanced replication, DataGuard or Logical
> Standby within the Oracle technology stack. Replication can be set up so that
> the remote site is an exact duplica of the local site, or as a master slave type
> relationship. DataGuard (the old standby database from Oracle8 days) allows a
> number of different levels at which data can be copied to the remote site,
> ranging from redo log shipping at the coarsest level to synchronous log vector
> shipping at the finest level of granularity. Logical Standby is something I
> haven't looked at a lot yet (it comes with 9i Release 2) but from what I
> understand of it it's basically a way of subsetting what is applied to the
> remote site.
You can also achieve machine and site failover together without using
replication. For example:
Two sites, on both of them is one server and one EMC storage. Both
sites are connected through fast line and everything is configured as
one Storage Area Network. EMC storages are mirroring each other.
So when one site goes down, other one can work with almost no
downtime. There is no need for replication, stand-by etc., because
data exchange between nodes is done by EMCs.
--
_________________________________________
Dusan Bolek, Ing.
Oracle team leader
Note: pagesflames_at_usa.net has been cancelled due to changes (maybe we
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Received on Fri Jun 07 2002 - 05:53:31 CDT
