Re: Data replication mechanisms?

In article <1e8276d6.0206070253.f0fb5e1_at_posting.google.com>, pagesflames_at_usa.net says...
>
>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
>can call it an overture to bankruptcy) on that server. I'm still using
>this email to prevent SPAM. Maybe one day I will change it and have a
>proper mail even for news, but right now I can be reached by this
>email.

Right, this can be done on other ways too, such as using EMC's SRDF product. For Oracle to support SRDF though, it must be running in syncrhonous mode, which can then cause some performance issues. From memory, even semi-synchronous is not supported.

There's more than one way to skin this cat.

HTH. Additions and corrections welcome.

Pete

SELECT standard_disclaimer, witty_remark FROM company_requirements; Received on Fri Jun 07 2002 - 13:14:49 CDT